Undrawn, tough, durably melt-bondable, macrodenier, thermoplastic, multicomponent filaments

ABSTRACT

Undrawn, tough, durably melt-bondable, macrodenier, thermoplastic, multicomponent filaments, such as sheath-core and side-by-side filaments, comprising a first plastic component and a second lower-melting component defining all or at least part of the material-air boundary of the filaments. The filaments can be made by melt-extruding thermoplastics to form hot filaments, cooling and solidifying the hot filaments, and recovering the solidified filaments without any substantial tension being placed thereon. Aggregations of the filaments can be made in the form of floor matting and abrasive articles.

This is a division of application Ser. No. 08/450,310 filed May 25,1995, now abandoned.

This invention relates to melt-extruded, melt-bondable, thermoplasticfilaments or fibers, particularly multicomponent fibers, such asbicomponent fibers of the sheath-core type, precursor thermoplasticpolymers therefor, and articles of such filaments or fibers, such asopen, nonwoven webs useful in the form of entry-way floor matting orabrasive pads. In another aspect, this invention relates to methods ofmaking said filaments or fibers and articles thereof. In a still furtheraspect, this invention relates to thermoplastic alternatives forpoly(vinyl chloride).

BACKGROUND OF THE INVENTION

Fibers based on synthetic organic polymers have revolutionized thetextile industry. One manufacturing method of fiber formation is meltspinning, in which synthetic polymer is heated above its melting point,the molten polymer is forced through a spinneret (a die with many smallorifices), and the jet of molten polymer emerging from each orifice isguided to a cooling zone where the polymer solidifies. In most instancesthe filaments formed by melt spinning are not suitable textile fibersuntil they have been subjected to one or more successive drawingoperations. Drawing is the hot or cold stretching and attenuation offiber filaments to achieve an irreversible extension and to develop afine fiber structure. Typical textile fibers have linear densities inthe range of 3 to 15 denier. Fibers in the 3 to 6 denier range aregenerally used in nonwoven materials as well as in woven and knittedfabrics for use in apparel. Coarser fibers are generally used incarpets, upholstery, and certain industrial textiles. A recentdevelopment in fiber technology is the category of microfibers withlinear densities <0.11 tex (1 denier). Bicomponent fibers, where twodifferent polymers are extruded simultaneously in either side-by-side orskin/core configurations, are also an important category of fibers.Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Ed., John Wiley& Sons, N.Y., Vol. 10, 1993, "Fibers," pp. 541, 542, 552.

A type of bicomponent fiber is the bicomponent binder fiber, thehistorical paper by D. Morgan which appears in INDA Journal of NonwovenResearch, Vol. 4(4), Fall 1992, pp. 22-26. This review article says itis worth noting that the majority of bicomponent fibers so far made havebeen side-by-side acrylics used in knitwear garments to provide bulk.Table 1 of this review article lists suppliers of various bicomponentfibers, which are of relatively low denier, ranging from about 1 to upto 20.

U.S. Pat. No. 4,839,439 (McAvoy et al.) and U.S. Pat. No. 5,030,496(McGurran) describe nonwoven articles prepared by blending meltbondable, bicomponent sheath/core, polyester, staple fibers having adenier of six and larger, for example 15, with synthetic, organic,staple fibers, forming a nonwoven web from the blend, heating the web tocause the melt bondable staple fibers to initially bond, or prebond, theweb, coating the web with a binder resin, and drying and heating thecoated web.

U.S. Pat. No. 5,082,720 (Hayes) discusses prior art relating to nonwovenwebs of bicomponent melt-bondable fibers. The invention of the Hayespatent is directed to drawn or oriented, melt-bondable, bicomponentfilaments or fibers of 1 to 200 denier formed by the co-spinning of atleast two distinctive polymer components, e.g., in a sheath-core orside-by-side configuration, immediately cooling the filaments after theyare formed, and then drawing the filaments. The first component ispreferably at least partially crystalline polymer and can be polyester,e.g., polyethylene terephthalate; polyphenylenesulfide; polyamide, e.g.,nylon; polyimide; polyetherimide; and polyolefin, e.g., polypropylene.The second component comprises a blend of certain amounts of at leastone polymer that is at least partially crystalline and at least oneamorphous polymer, where the blend has a melting point of at least 130°C. and at least 30° C. below the melting point of the first component.Materials suitable for use as the second component include polyesters,polyolefins, and polyamides. The first component can be the core and thesecond component can be the sheath of the bicomponent fiber.

Filaments of poly(vinylchloride) ("PVC," or simply "vinyl"), a syntheticthermoplastic polymer, are used to make open or porous, nonwoven,three-dimensional, fibrous mats or matting. The mats are used forcovering any of a variety of floors or walking surfaces, such as thoseof office building, factory, and residential entry-ways or foyers andhallways, areas around swimming pools, and machine operator stations, toremove and trap dirt and water from the bottom (soles and heels) ofshoes, protect floors and carpets, reduce floor maintenance, and providesafety and comfort. Generally the mats are open or porous webs ofinterengaged or intertwined, usually looped, sinuous, or coiled, coarseor large-diameter fibers (or filaments); such fibers are typicallymelt-extruded from plasticized PVC into single-component fibers whichare aggregated and bonded (usually with an applied binder coating oradhesive). An example of commercially-available matting product isNomad™ matting constructed of interengaged loops of vinyl filaments thatare bonded together and may be supported on and adhered to abacking--see product bulletins 70-0704-2684-4 and 70-0704-2694-8 of the3M Company, St. Paul, Minn., U.S.A.

Relatively early patents describing matting made from variousthermoplastics including PVC are U.S. Pat. No. 3,837,988 (Hennen etal.), U.S. Pat. No. 3,686,049 (Manner et al.), U.S. Pat. No. 4,351,683(Kusilek), and U.S. Pat. No. 4,634,485 (Welygan et al.). Common aspectsof the method described in these patents, briefly stated, comprisesextruding continuous filaments of thermoplastic polymer downward towardand into a water quench bath where a web of interengaged, integrated, orintermingled and spot-bonded filaments is formed. The web can besubsequently treated with bonding agent or resin to improve bonding,strength, or integration. Typically, in the absence of a bonding agentor resin applied and cured subsequent to the web-forming step, thefilaments of the web exhibit a tensile strength much greater than thatof the spot-bond itself. That is, as a result of tensile force appliedto the web after spot welding but before application of a subsequentbonding treatment, the fibers of the web will separate at the sites ofinterfilament bonding more frequently than the fibers will break.

Recently poly(vinyl chloride) has been said to be environmentallyundesirable because its combustion products include toxic or hazardoushydrogen chloride fumes. It has been reported that the existing use ofPVC in Sweden should be phased out by the year 2000--see EuropeanChemical News, Jul. 4, 1994, p. 23. One Swedish commercial enterprisestated it plans to stop making PVC-based elastic flooring and launch anew, PVC-free flooring--see Plastic Week, Aug. 9, 1993. Thus attentionis being directed to alternatives for PVC.

Bicomponent fibers and multicomponent fibers are described inKirk-Othmer Encyclopedia of Chemical Technology, Third Ed., SupplementVol., 1984, pp. 372-392, and Encyclopedia of Polymer Science andTechnology, John Wiley & Sons, N.Y., Vol. 6, 1986, pp. 830, 831. Patentsdescribing certain multicomponent or bicomponent fibers include U.S.Pat. Nos. 3,589,956 (Kranz et al.), 3,707,341 (Fontijn et al.),4,189,338 (Ejima et al.), 4,211,819 (Kunimune), 4,234,655 (Kunimune etal.), 4,269,888 (Ejima et al.), 4,406,850 (Hills), 4,469,540 (Jurukawaet al.), 4,500,384 (Tomioka et al.), 4,552,603 (Harris et al.),5,082,720 (Hayes), 5,336,552 (Strack et al.). The process of manufactureof multicomponent fibers and a general discussion of the method ofextrusion of these fibers are also described in Kirk-Othmer, Third Ed.,loc. cit. Some patents describing spinneret assemblies for extrudingbicomponent fibers of the sheath-core type are U.S. Pat. Nos. 4,052,146(Sternberg), 4,251,200 (Parkin), 4,406,850 (Hills), and PCTInternational Appln. published as WO 89/02938 (Hills Res. & Devel.Inc.).

Some other patent filings, viz., U.S. Pat. Nos. 3,687,759 (Werner etal.) and 3,691,004 (Werner et al.), though they do not describe PVCmatting, describe mattings of filaments of substantially amorphouspolymer, such as polycaprolactam, which are formed by melt spinning intoa liquid quench bath in such a manner that the filaments lie in the formof overlapping loops randomly bonded at their points of contact as theysolidify in the bath. These patents state that preferably the filamentsare spun, looped, and bonded without any substantial tension beingplaced on the filaments, or that it is preferable to avoid anysubstantial tension capable of stretching the filaments as they arewithdrawn through the cooling bath so that the amorphous character ofthe initial polymer is largely retained. Matting articles which areformed without spinning into a liquid quench bath and consistingessentially of melt-spun filaments which are self bonded or fused atrandom points of intersection without using any bonding agent have beendescribed in U.S. Pat. No. 4,252,590 (Rasen et al.).

A series of patents issued to Yamanaka et al., viz., U.S. Pat. Nos.4,859,516, 4,913,757, and 4,95,265, describe various mats consisting offilament loop aggregations formed by extruding thermoplastic syntheticresin vertically toward the surface of a cooling bath of water at aspeed regulated by guide rollers disposed in the water (to which asurface active agent can be added), the density of the aggregations ofthe resulting bonded or fused aggregations being regulated in certainmanners.

SUMMARY OF THE INVENTION

This invention, in one aspect, provides undrawn, tough, durablymelt-bondable, thermoplastic, macrodenier, multicomponent filamentcomprising, consisting, or consisting essentially of the followingcomponents:

(a) first plastic comprising synthetic organic plastic polymer,preferably a thermoplastic, which can be semicrystalline, such as nylon6; and

(b) second plastic comprising synthetic organic thermoplastic polymer,such as ethylene-vinyl acetate copolymer or a blend of an ethylene-vinylacetate copolymer and an ethylene-methyl acrylate copolymer, which meltsupon heating at a temperature lower than the temperature which meltscomponent (a), e.g., at least 15° C. lower, preferably 30° C. lower, andis generally amorphous or semicrystalline;

said components (a) and (b) being, along the length of the filament,elongated, contiguous, coextensive in length, and, preferably, integraland inseparable (e.g., in boiling water), said component (b) definingall or at least part (e.g., 5 to 90%, preferably 20-85%) of thematerial-air boundary or peripheral or external surface of the filament.The plastic of each of said components (a) and (b) can be a singleplastic substance or a blend of a plurality of plastic substances andcan consist or consist essentially of such plastic substances. Saidcomponents can further comprise or have incorporated adjuvants oradditives to enhance a property of or impart a property to the filament,such as stabilizers, processing aids, fillers, coloring pigments,crosslinking agents, foaming agents, and fire retardants. The filamentcan comprise a plurality, e.g., 2 to 5, of components (a) and/or ofcomponents (b), a preferred multicomponent filament being a bicomponentfilament, such as a sheath-core or side-by-side filament.

Another aspect of this invention provides a method of making theabove-described multicomponent filaments. Such method comprisescontinuous steps of simultaneously (or conjointly) melt-extruding,preferably at the same speed, molten streams of thermoplastic polymers(some of which are novel blends of polymers) as precursors of components(a) and (b) via one or a plurality, e.g., 1 to 2500, preferably 500 to1800, extruder die openings or orifices, in the form of a single or aplurality of discrete and separate hot, tacky, molten, multicomponentfilaments, cooling them, for example, in a water quench bath, andrecovering the resulting non-tacky, solidified filaments, for example,as a tow or web of such filaments.

In another aspect of this invention, a plurality of the above-describedsolidified filaments are self-bonded to one another by heating anaggregation thereof, e.g., in the form of an open, nonwoven web of thefilaments in a coiled form, to or above the melting point of component(b) in order to effect durable melt-bonding at filament surfaces incontact with melted component (b), and thereby provide a sufficientlybonded aggregation of the filaments, e.g., an open, nonwoven web ofdurably melt-bonded, undrawn, tough, macrodenier, multicomponentfilaments. Such bonding can be accomplished without requiring or using acoating or otherwise applying to the filaments a binder resin, solvent,or extra adhesive or mixing the filaments with so-called binder fibers,though such materials may be used to supplement the self-bonding of thefilaments.

The filaments of this invention, following their melt-extrusion andcooling to a solidified form, are not subsequently or additionallydrawn, that is, stretched, pulled, elongated, or attenuated. Incontrast, textile fibers, including bicomponent textile fibers, arecommonly drawn as much as, for example, 2 to 6 or even 10 times theiroriginal length, usually to increase their strength or tenacity.

The filament of this invention, as that term is used herein, is anelongated or slender article which is narrow or small in width, crosssection, or diameter in proportion to its length. Generally the filamentcan have a width, diameter, or cross-section dimension of at least 0.2mm, preferably at least 0.4 mm, which dimension generally will be in therange of 0.5 to 25 mm, preferably 0.6 to 15 mm, such dimension (andshape of the cross section) being preferably substantially oressentially uniform along the length of the filament, e.g., uniformlyround. The surface of the filament is typically smooth and continuous.Because the filament is larger in cross section in comparison tobicomponent textile-size or textile-denier filaments or "fine" fibers(which are generally considered to be 1 to 20 denier per fiber or"dpf"), the filament of this invention is relatively coarse and can becharacterized (especially as compared to textile fibers) as being orhaving a macrodenier (and can even be characterized as being amacrofilament). Generally the filament of this invention has a lineardensity greater than 200 dpf and as much as 10,000 dpf or more, e.g., upto 500,000 dpf, but preferably the filaments of this invention havelinear densities in the range of 500 to 20,000 dpf.

The multicomponent filaments of this invention can be in the shape orform of fibers, ribbons, tapes, strips, bands, and other narrow and longshapes. Aggregations of the filaments, such as open, nonwoven webs, canbe made up of a plurality of filaments with the same or differentplastic compositions, geometric shapes, sizes and/or deniers. Aparticular form of such filaments is side-by-side (or side-side)bicomponent filaments or, preferably, sheath-core (or sheath/core)bicomponent filaments, each comprising said components (a) and (b) withone or more (e.g., 1 to 9) interfaces between the components and withthe material-air boundary of the filament defined at least in part by anexternal surface of component (b). In a typical sheath-core filament,the sheath, component (b), provides a matrix (with a continuous externalsurface, the filament's material-air boundary) for one or morecomponents (a) in the form of cores. The filaments can be solid, hollow,or porous and straight or helical, spiral, looped, coiled, sinuous,undulating, or convoluted. They can be circular or round in crosssection or non-circular or odd in cross section, e.g., lobal,elliptical, rectangular, and triangular. They can be continuous inlength, that is, of indefinite length, or, by cutting them in that form,they can be made in a short, discontinuous, or staple form of definitelength. The components (a) and (b) can be solid or noncellular, or oneor both components can be cellular or foamed with open and/or closedcells. Both of the components (a) and (b) can have the same form orshape or one of them can have one form or shape and the other componentcan have a different form or shape.

In characterizing the multicomponent filament of this invention asdurably melt-bondable, this means that a plurality or aggregation ofsuch filaments, such as an open, non-woven web, can be bonded togetherat their points of contact or intersection to form aninterfilament-bonded structure by heating the filaments sufficiently toor above the melting point of their component (b) in order to meltcomponent (b) without melting their component (a), and then cooling thefilaments to solidify component (b), thereby causing the filaments tobecome bonded, to one another by a bond of component (b) at each oftheir contiguous material-air boundaries, points of contact, orintersections. Such melt-bonding of the filaments is a self-bonding inthat it is effected without using or requiring the application of anexternal bonding agent, or solvent, or adhesive coating applied to thefilaments or mixing so-called binder fiber therewith. This self-bondingfeature is thus an environmental or cost advantage of the filaments ofthis invention vis-a-vis those known filaments or fibers that use orrequire such agent, solvent, coating, or binder fiber for bonding. Thisself-bonding may additionally be characterized and differentiated fromspot- or tack-bonding, spot welding, or removably-welding by thestrength of the bond formed. The melt-bond achieved by the filaments ofthis invention is a durable bond in that it is sufficiently strong orfracture resistant that interfilament melt-bond strength generally is atleast as great as that of the strength of the filament itself, andgenerally the melt bond strength exceeds 1.4 MPa, and preferably is atleast 4.8 MPa (ca 700 psi), based on the cross-section area of thefilament before breaking stress is applied thereto. In a tack-bondedstructure, such as that of an open, nonwoven web of coiled filaments,tack-bonded filaments can be relatively easily separated from thestructure, e.g., by a pulling stress of less than 0.02 MPa (ca 3 psi),based on the cross-section area of the filaments before breaking stressis applied thereto, without distorting or breaking the filamentsthemselves. The fact that melt-bonded filaments of this inventionthemselves break, rather than their melt-bonds, attests to the durablymelt-bondable character of the filaments (as well as to the durablemelt-bonded character of a melt-bonded aggregration of the filaments,such as an open nonwoven web). Furthermore, the multicomponent nature ofthe filaments provides an unexpected advantage by allowing component (a)thereof to provide a structural role in supporting the shape of the webof such filaments in either a post-formation melt-bonding step.

Because the filaments of this invention are self- or melt-bondable, websformed from the melt-bonded filaments of this invention are durablewithout requiring the application of binding agent, or adhesive coating,or solvent and can be used for article fabrication once the webs aremelt-bonded. Contrariwise, many nonwoven webs made in whole or part fromso-called binder fiber, which are typically textile-size fibers, e.g., 3to 15 dpf, are often additionally bonded, strengthened, or reinforcedwith binder resins that are roll- or spray-coated on thethermally-bonded web, especially when durability and toughness areneeded.

The multicomponent filaments of this invention may be fabricated intofilamentary articles or structures or three-dimensional aggregationscomprising a plurality of the filaments, which can be in eithercontinuous or staple form. For example, said aggregations may be in theform of open, permeable or porous, lofty webs or batts of interengaged,intertwined, interlocked, or entangled filaments or twisted, woven, orbraided filaments that can be generally straight or helical, spiral,looped, coiled, curly, sinuous or otherwise convoluted filaments whichcan extend from one end of the web to the other end. The contiguousmaterial-air boundaries of the filaments can be melt-bonded at theirpoints of intersection or contact to form a water permeable, lofty orlow bulk density, unitary, monolithic, coherent or dimensionally-stable,three-dimensional filamentary structure or mass, such as an open,nonwoven web, minimal, or any, melted thermoplastic filling up theinterfilament gaps or interstitial spaces of the structure. Webs can becut to desired sizes and shapes, for example, in lengths and widthsuseful, for example, as floor covering or door mats for buildingentrances and other walkway surfaces. If desired, the web can be firstmelt-bonded on one side to suitable backing, such as a thermoplasticsheeting, prior to cutting into mats. Such masses, aggregations, orstructures, when used as matting, provide resilient cushioning in theform of lofty, open, low bulk density, pliable mats or pads to coverfloors or walking surfaces to protect the same from damage by dirt,liquid, or traffic wear, to provide safety and comfort to those peoplewho walk or stand thereon, and to improve the aesthetic appearance ofsuch substrates. Such mats can be stood or walked upon by people over avery long time with comfort and safety and without losing theirdurability. The mats are preferably of such low bulk density or highvoid volume that, in holding them up to a light source, light can beseen therethrough and dirt or water tracked thereon readily falls orpenetrates therethrough. Generally, such mats can be used where PVCmatting has been or can be used and as an alternative thereto, and,specifically, for those applications described in the above-cited 3MCompany bulletins, which descriptions are incorporated herein byreference. The filamentary mass or web of this invention can also beused as a spacer or cushioning web, a filter web, as the substrate ofscouring pads, erosion-control or civil engineering matting forretaining soil on embankments, dikes, and slopes and the like to protectthem from erosion, as a substrate or carrier for abrasive particles andthe like, and as a reinforcement for plastic matrices.

The multicomponent filaments of this invention can be fabricated withindeterminate length, that is, in truly continuous form and, if desired,made as long in length as the supply of melt precursor or feed thereoflasts and having a length dependent only on the limitations of thefabricating equipment. Webs formed from these continuous filaments canbe readily cut to desired dimensions, for example, after they areintertwined or intermeshed as looped or coiled, bonded filaments in theform of an open, nonwoven web or matting. Alternatively, thesecontinuous filaments can be cut into staple length fibers, for example,2.5-10 cm in length, and such short lengths can used, for example, in abonded aggregation as a substrate for abrasive cleaning and polishingpads in applications like those whose fabrication is described in saidU.S. Pat. No. 5,030,496 and U.S. Pat. No. 2,958,593 (Hoover et al.),which descriptions (except for the requirement of an adhesive coating)are incorporated herein by reference.

Preferably the filaments of this invention are melt-extruded as a bundleor group of free falling, closely spaced, generally parallel, discrete,continuous, multicomponent filaments of hot, tacky, deformable, viscouspolymer melts, for example, as sheath-core bicomponent fibers, the hotfilaments then being quickly cooled, or quenched, to a non-tacky ornon-adhesive solid state. The hot filaments can be so-cooled or quenchedto form a tow of non-tacky, essentially solid, discrete continuousfilaments by contact with a cooling means or medium, such as a liquidquench bath, e.g., a body of water. The tow can then be advanced orconveyed through the bath and withdrawn therefrom. The tow may then befurther cooled, if desired. The tow can be used to fabricate nonwovenpads, such as those whose fabrication is described in U.S. Pat. No.5,025,591 (Heyer et al.), used for scouring pots and pans, etc., or thetow can be cut into staple lengths which can be used to make abrasivepads, such as those whose fabrication is described in U.S. Pat. No.2,958,593 (Hoover et al.), which descriptions (except for therequirement of an adhesive coating) are incorporated herein byreference. If the speed at which the tow is withdrawn from the quenchbath, i.e., the take-away speed, is equal to or greater than the speedof the hot filaments entering the quench bath, the tow will compriseessentially straight, non-coiled, non-convoluted, discrete filaments.

A tow comprised of helically shaped, coiled, or convoluted, discrete,continuous, multicomponent filaments, one such filament being shown inFIG. 4, can be formed in the above-described fashion if the tow isconveyed through the quench bath at a take-away speed which is less thanthe speed of the filaments entering the quench bath so as to permit thefalling, molten, still deformable filaments to coil into an essentiallyhelical shape adjacent the surface of the quench bath. The free-fallingmolten filaments preferably are sufficiently spaced-apart to preventindividual filaments from interfering with the coiling action ofadjacent filaments. The use of a surfactant (for example, as describedin said U.S. Pat. No. 3,837,988) in the quench bath may be desirable toaid coil formation.

A web of coiled, multicomponent filaments can be formed by permittingthe bundle of melt-extruded, free-falling filaments to (i) deform, coil,wind, or oscillate in a sinuous manner, (ii) interengage, intertwine, oraggregate in a desired ordered or random pattern to a desired webweight, (iii) tack- or spot-bond upon contact with each other, and (iv)immediately thereafter cool to a non-tacky, solid state. Thefree-falling molten filaments in the bundle are sufficientlyspaced-apart to allow intermingling of the coiling and overlappingfilaments. The take-away speed of the web preferably is sufficientlyslow relative to the speed of the filaments entering the quench bath soas to allow the falling, coiling filaments to aggregate adjacent thesurface of the quench bath as described in said U.S. Pat. No. 4,227,350or alternatively to aggregate on one or more contact surfaces adjacentthe surface of the quench bath. The contact surface(s) may be in motion,as for example the surface of a rotating cylindrical drum as describedin said U.S. Pat. No. 4,351,683, so as to collect the newly-forming weband help convey it into and/or through the quench bath. The substratemay alternatively be stationary, for example, a plate as described insaid U.S. Pat. No. 3,691,004. (Said descriptions of said U.S. Pat. Nos.4,227,350, 4,351,683, and 3,691,004 are incorporated herein byreference.) The lightly-unified web thus formed comprises overlapping orentangled loops or coils of filaments and has sufficient structuralintegrity to allow the web to be conveyed, transported, or otherwisehandled. The web can be dried and stored if necessary or desired priorto the melt-bonding step. This melt-bonding step involves heating thelightly-unified web to cause melting of the lower-melting plastic ofcomponent (b) without deforming component (a), and then cooling the webto re-solidify component (b) in order to effect melt-bonding at pointsof intersection of the filaments to form an open, durably melt-bondedweb.

In the above-described methods of fabricating multicomponent filamentsof this invention, unlike methods commonly used to manufacture singlecomponent or bicomponent fibers, such as textile fibers, themulticomponent filaments of this invention, as stated above, areundrawn. That is, the filaments of this invention are not mechanically,aerodynamically, or otherwise drawn, stretched, or pulled after they arequenched. The filaments, after having been quenched, are not attenuated,as for example, with a mechanical draw unit, air aspirator, air gun, orthe like, so as to reduce their diameter, width, or cross-sectionalarea. After the hot filaments are cooled and solidified from their hot,tacky, molten state to their non-tacky, solidified state, theirdiameters, widths, or cross-sectional areas and shape remainsubstantially or essentially the same in their finished state, that is,after tow collection or web formation and subsequent melt-bonding steps,as when first cooled to the solid state. In other words, although thecooled and solidified filaments can be thereafter aggregated,melt-bonded, conveyed, wound, or otherwise handled or processed, suchhandling is done in a relatively relaxed manner without any substantialtension being placed on the solidified filaments. Thus, once solidified,the filaments of this invention are processed in an essentiallytension-less manner, without substantial or significant attenuation, sothat their denier or magnitude after processing to their finished formcan be essentially the same as that upon first cooling the viscousfilaments; consequently, the filaments are said to be undrawn.

Notwithstanding the multicomponent filaments of this invention areundrawn, they are tough, that is, strong and flexible but not brittle orfragile, and the melt-bonded aggregations of such filaments are durable,that is, resistant to fatigue due to constant flexing, even though theirbonding is achieved without use of an added or applied bonding oradhesive agent, such as coating with an adhesive coating solution ormixing the filaments with added known binder fibers. In contrast todrawn fibers, the cooled, solidified filaments of this invention can bereadily stretched or drawn by grasping such a filament by two hands--oneon each end of a segment (e.g., 10 cm long)--and pulling the segmentbetween them, for example, to 2 or more times its initial length,thereby attenuating the filament diameter or cross-sectional area.

Because of the non-PVC thermoplastics which can be used to fabricate themulticomponent filaments of this invention, environmental regulationswhich restrict the use of PVC will not necessarily be applicable to thefabrication, use, or disposal of the filaments of this invention.Another environmental advantage is that no adhesive or volatile solventsare required to durably bond the filaments of this invention in the formof a unitary or monolithic structure, such filaments beingself-bondable, that is, melt-bonding at their contiguous material-airboundaries or surfaces that arc heated to melt the lower melting plasticof component (b) of such filaments and thermally bond the same at saidboundaries or surfaces.

BRIEF DESCRIPTION OF THE DRAWING

In the accompanying drawing, which depicts or illustrates someembodiments and or features of this invention, and where like referencenumbers designate like features or elements:

FIG. 1A is a schematic view in elevation and partial cross-sectionshowing one embodiment of apparatus that can be used to make a tow ofstraight or uncoiled, multicomponent filaments of this invention;

FIG. 1B is a schematic view in elevation and partial cross-sectionshowing another embodiment of apparatus that can be used according tothis invention to make coiled multicomponent filaments and an open,nonwoven web thereof;

FIGS. 1C and 1D are schematic views in elevation and partialcross-section showing embodiments of apparatus that can be used to makebacked, open, nonwoven webs of coiled multicomponent filaments inaccordance with this invention;

FIG. 2A is a schematic view in elevation and cross section of a portionof an extruder die assembly useful in the apparatus of FIGS. 1A-1D formelt-extruding sheath-core filaments of this invention;

FIG. 2B is a enlarged view in cross section of a portion of FIG. 2A;

FIG. 3 is a enlarged view of a portion of FIG. 1B;

FIG. 4 is a schematic isometric view of a single multicomponent filamentof this invention in its helical or coiled form;

FIG. 5 is a schematic view in elevation and cross section of a portionof another extruder die assembly useful in the apparatus of FIGS. 1A-1D;

FIG. 6 is a partial cross-section and enlarged view of FIG. 5 takenalong the line 6--6 thereof;

FIGS. 7 to 14 are schematic cross-sections of sheath-core multicomponentfilaments of this invention;

FIGS. 15 to 17 are schematic cross-sections of side-by-sidemulticomponent filaments of this invention;

FIG. 18 is a schematic cross-section of a bundle of unbonded,contiguous, sheath-core filaments of this invention;

FIG. 19 is a schematic cross-section showing the bonding of thefilaments of FIG. 18;

FIG. 20 is a schematic perspective view of portions of two unbondedcontiguous sheath-core filaments of this invention;

FIG. 21 is a schematic perspective view showing the bonding of thefilaments of FIG. 20 at their points of contact;

FIG. 22 is a schematic view in perspective of a portion of a filamentarymatting of this invention;

FIG. 23 is a schematic cross-section in elevation of a portion of afilamentary matting of this invention which is bonded to a backing;

FIG. 24 is a schematic isometric view of a portion of a matting of thisinvention which is embossed on one side with a grid of channels;

FIG. 25 is a schematic isometric view of a portion of bonded filamentsof this invention showing a broken filament and the residue of a brokenmelt-bond; and

FIG. 26 is an isometric view of abrasive-coated filaments of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawing, and initially to FIG. 1A, a firstthermoplastic polymer composition, to be used to form component (a) ofbicomponent filaments of this invention, is fed in pellet, crumb, orother form into the hopper 10a of a melt extruder 11a, from which astream of polymer melt (e.g., at 100° to 400° C.) is fed, optionallyunder pressure of a metering pump 12a, into a bicomponent extrusion dieassembly 13. Similarly, a second thermoplastic polymer composition to beused to form component (b) of the bicomponent filaments is fed into thehopper 10b of melt extruder 11b, from which a stream of polymer melt isfed, optionally under pressure of metering pump 12b, into the extrusiondie assembly 13. Examples of equipment for extruding bicomponent fibersare described in Kirk-Othmer, Third Ed., Supp. Vol. supra, p. 380-385.Examples of extrusion die assemblies in the form of spinnerets aredescribed in U.S. Pat. Nos. 4,052,146 (Sternberg), 4,406,850 (Hills) and4,251,200 (Parkin), PCT Appln. WO 89/02938 (Hills Research andDevelopment Inc.), and Brit. Pat. 1,095,166 (Hudgell). Examples ofextrusion dies are described by Michaeli, W. in Extrusion Dies, Designsand Computations, Hanser Pub., 1984, pp. 173-180. These descriptions oftechnology are incorporated herein by reference, and the equipmenttherein can be modified in dimensions and configuration by those skilledin the art for use in extruding the macrodenier, multicomponentfilaments of this invention in light of the description of it herein.

FIGS. 2A and 2B illustrate the bicomponent, filament, extrusion dieassembly 13 of FIG. 1A, such assembly being made of a number of machinedmetal parts having various chambers, recesses, and passages for the flowof molten thermoplastic and rigidly held together by various means (notshown in the drawing), such as bolts. Assembly 13 comprises adual-manifold of the slit type made up of mating blocks 14a and 14b eachhaving a manifold passage disposed therein and separated by a verticalplate 15. Manifold blocks 14a and 14b are provided with opposingrecesses at the lower ends in which is inserted a mating pair of prelipblocks 16a, 16b with flared, opposed inner surfaces separated by thelower portion of plate 15. Blocks 14a, 14b surmount a lower die holder25 having a recess to accommodate an inserted extrusion die pack 26 ofthe castellation type and comprising stacked plates, viz., top plate 18,center or distribution plate 19, and lower or orifice plate 20 fromwhich issue hot, viscous, tacky, sheath-core filaments formed in thepack. Viscous core polymer composition, component (a) of the filaments,is caused to flow from a feed passage 22a within manifold block 14a todistribution manifold passage 22b and thence into chamber 22c in topplate 18 that functions as a local manifold from which the core polymermelt flows into an array of vertical core flow passages 23 in plate 19.Viscous sheath polymer composition, component (b) of the filaments, issimultaneously caused to flow from a feed passage 24a within dualmanifold block 14b to a second polymer distribution manifold passage 24band thence into a second and separate chamber 24c in top plate 18 thatfunctions as a local manifold from which the sheath polymer melt flowsdownwardly through a rectangular channel (shown by the broken line) incenter plate 19 to a horizontal recess or cavity 24d disposed betweencenter plate 19 and orifice plate 20. The latter has an array ofcircular vertical channels 27 axially aligned with core flow passages23. Channels 27 communicate at their upper ends with recess 24d andterminate at their lower ends with extruder nozzles having orifices 28.As shown clearly in FIG. 2B, the upper face of the orifice plate 20defining the bottom of recess 24d is machined with an array of raised,circular protuberances, buttons, or castellations 29, each surroundingthe upper or inlet end of a channel 27 and defining a fine gap 30between their upper surface and the lower face of distribution plate 19(or top of recess 24d) to ensure uniform sheath thickness. The sheathmelt flows in fine gap 30 and enters channels 27 around the respectivestreams of core melt flowing from passages 23 into the cores of thechannels so that bicomponent sheath-core filaments issue from orifices28, the cross section of such a filament being shown in FIG. 7.

Referring again to FIG. 1A, the extruder die assembly 13 continuouslyextrudes downwardly, in relatively quiescent air, a plurality or bundle31 of hot, viscous, tacky, closely-spaced, discrete, continuous,macrodenier, multicomponent filaments 32 which fall freely into a bodyor bath 33 of quench liquid, such as water, in an open-top tank 34. Thesurface 35 of the bath 33 is disposed a suitable distance below thelower face of the extrusion die assembly 13 in order to maintain thediscrete nature of falling filaments in the zone of cooling air abovethe bath. The bundle 31 upon entering the bath 33 is quickly cooled orquenched from the extrusion temperature, e.g., 100 to 400° C., down toabout 50° C., and solidified to a non-tacky state. The discrete,quenched filaments 32 are continuously gathered or collected and areguided around turnaround roll 36 as a tow 30 which is conveyed by a pairof pinch rolls 37a and 37b out of the bath. The tow 30 may then be woundon winder 38 to form a tow winding 40.

In a similar fashion, referring now to FIG. 1B, the extruder dieassembly 13 (which, as in FIG. 1A, is connected to extruders andoptionally to metering pumps, not shown in FIG. 1B) extrudes downwardlya plurality or bundle 41 of hot, viscous, tacky, closely-spaced,discrete, continuous, macrodenier, multicomponent filaments fibers 42which fall freely in the quiescent ambient air into tank 34. The bundle41 can be aligned so that some of the hot, viscous filaments 42 arepermitted to make glancing contact with the outer surface of a guideroll 39, optionally provided with spaced-apart guide pins or pegs 47(see FIG. 3), or some other type of guide, such as a stationery plate,to guide the hot, viscous filaments as they move toward the surface 35of a body or bath 33 of quench liquid, such as water, in tank 34, thesurface of the liquid being disposed a suitable distance below the lowerface of the extruder die assembly of 13 so as to achieve the desireddiameter of the filaments as they enter the bath. The roll 39 can be setto cause glancing contact with the filaments 42, as described in saidU.S. Pat. No. 4,351,683, which description is incorporated herein byreference. As the hot, viscous filaments 32 fall in the ambient air,they begin to cool from the extruding temperature (which can range, forexample, from 100° C. to 400° C.). The guide roll 39 (as well asoptional roll 48 and other rolls downstream) can be set to rotate at apredetermined speed or rate such that the rate of lineal movement of thefilaments 42 as they enter the body 33 of quench liquid is slower thanthe rate of linear movement of the hot, viscous filaments upstream ofthe guide roll(s). Since the take-away speed is slower than the speed ofthe hot filaments entering the quench bath 33, and the filaments 42 arestill in a sufficiently viscous, deformable, or molten state, thefilaments accumulate or aggregate themselves by coiling, undulating, oroscillating and interengaging just above the surface 35 of the quenchliquid 33 into which they enter and can further cool, e.g., to about 50°C., quickly enough so that their shape does not deform, and solidify orrigidify just below the surface 35. A degree of resistance is impartedto the flow or free fall of the hot, viscous filaments 42 above thesurface 35 by the already quenched, aggregated filaments in the quenchbath 33 below its surface, which causes the still deformable filamentsentering the quench bath to coil, oscillate, or undulate just above thesurface of the bath. This motion establishes irregular or randomperiodic contact between the still-hot filaments, resulting in spot- ortack-bonding of contiguous surfaces of the filaments at their points ofcontact or intersection. Consequently, the filaments 42 assume a coiled,looped, sinuous, or undulating configuration and become interengaged asillustrated in FIG. 3, one such filament being shown in FIG. 4. Thefilaments 42 upon entering the quench liquid 33 and passing adjacentimmersed guide roll 39 form an integrated web 43 of lightly spot- ortack-bonded, solidified filaments.

The web 43 can be conveyed and withdrawn from the tank 34 by means ofpinch rolls 44a and 44b and wound by roll 45 to form a winding 46 of theweb. In this tack- or spot-bonded form, the filaments, thoughinterengaged and lightly bonded, generally can be individually andeasily pulled by hand from the web 43 and stretched to uncoil orstraighten them in continuous form under such hand-pulling and withoutattenuation, showing that their tack-bonding is not durable. The web 43can be unwound from winding 46 and placed in an air-circulating oven orthe like to heat the web to an appropriate temperature for a sufficienttime, e.g., 120° to 300° C., preferably 140° to 250° C., for 1 to 5minutes, and then cooled to room temperature (e.g., 20° C.) to causedurable melt-bonding of the contiguous surfaces of the filaments in theweb at their points of contact and form a finished, integral, unitaryweb with high void volume, e.g., 40 to 95 vol. %. The time andtemperature for this melt-bonding will be dependent upon selecting thedesired polymers for components (a) and (b) of the multicomponentfilaments.

Referring to FIG. 1C, a web of coiled filaments is fabricated as in FIG.1B, but the web is laminated with a thermoplastic backing as both areformed. For such lamination a separate extruder 11c, provided withhopper 10c, is used to provide a thermoplastic melt which is supplied toa film die 49 which extrudes a backing film or sheet 50 which cancomprise a thermoplastic of the types used to form filament component(b). Such film 50 is directly cast on roll 48 prior to the zone on roll39 that is also used to form a densified surface of filaments on theweb. Some of the downwardly-extruded, hot filaments that comprise thedensified portion of the web are laid down on the still hot, castbacking, thereby ensuring good bonding between the backing and the web.The resulting web-backing laminate 51 is conveyed to winder 46 toprovide a winding 52 of backed web, which can be placed in amelt-bonding oven to ensure durable melt-bonding.

Referring to FIG. 1D, a web of coiled filaments is also fabricated as inFIG. 1B, but an unheated or cool preformed backing 53, which can bethermoplastic of the types used for filament component (b), is suppliedby roll 54 and placed in contact by roll 48 with the hot web offilaments and tack-bonded to the surface thereof, the resultingweb-backing laminate 51 being conveyed by rolls 44a, 44b and wound byroll 46 to form a winding 52, which can also be melt-bonded in an oven.

FIGS. 5 and 6 illustrate a multicomponent, five-layer filament extrusiondie version of extrusion die assembly 13 of FIGS. 1A and 1B, the diepack 90 of this version comprising top plate 18, center distributionplate 96, and lower or orifice plate 97 from which issue hot, viscous,tacky, five-layer filaments formed in the pack. One such filament, withside-by-side alternate layers, is depicted in FIG. 15 and as havingthree layers 67 of component (b) separated by two layers 66 of component(a). Viscous polymer composition, used to form layers 67 of the filamentof FIG. 15, is caused to flow from feed passage 22a to feed manifold 22bto a chamber 94 in top plate 18 that functions as a local manifold fromwhich the polymer melt flows into an array of vertical flow passages 101each disposed outwards from a central channel 103 in center plate 96.Viscous polymer composition, used to form layers 66 of the filaments, issimultaneously caused to flow from feed passage 24a to feed manifold 24bto a chamber 93 in top plate 18 that functions as a local manifold fromwhich the polymer melt flows into an array of vertical flow passages 102disposed outwards from a central channel 104 in center plate 96.Channels 103 and 104 axially align with chambers 94 and 93,respectively. Lower plate 97 has an array of circular, vertical channels99 that is axially aligned with the center of a set of interposed arraysof vertical flow passages 101 and vertical flow passages 102. Channels99 communicate with the set of arrays of vertical flow passages 101 and102 and terminate at their lower ends with extrusion nozzles havingorifices 100. The upper face of orifice plate 97 is machined withrectangular countersunk depressions 98, each surrounding the upper orinlet end of a channel 99 and defining a cavity between its uppersurface and the lower face of distribution plate 96. The component meltstreams that will form layers 66 and 67 of the filament shown in crosssection in FIG. 15 flow through the passages 102 and 101, respectively,of plate 96, entering the cavity in plate 97, merging to form a singlemelt stream of five alternating layers and entering channel 99 so thatfive-layer, multicomponent filaments issue from orifices 100.

In general, the bulk density (or void volume), width, thickness, andloftiness of the webs made from filaments of this invention can bevaried by selecting the desired polymers and combinations thereof forforming the multicomponent filaments, the configuration or geometry anddimensions of the extrusion die pack (and the number, size, and spacingof the orifices thereof), and the speed of the various rolls used toconvey the web in the quench tank and to wind up the finished web.

Referring again to the accompanying drawing, FIGS. 7, 8, 9, 11, and 14illustrate the cross sections of round, circular or trilobal,sheath-core filaments of this invention, each with a single core 151 anda single sheath 152 with a single interface 153 between them. In FIG. 7,the core 151 and sheath 152 are concentric. In FIG. 8, the core 151 iseccentrically disposed within the sheath 152. In both FIGS. 7 and 8, thematerial-air boundary or peripheral surface 154 of the filaments isdefined by the exposed surface of the sheath 152. In FIG. 9, thematerial-air boundary 154 of the filament is defined in part by theperipheral surface of the sheath 152 and in part by an exposed portionof the core 151 (if that exposed portion were larger, the filament mightbe more properly called a side-by-side filament). In FIG. 14, the corecomponent 151 is essentially centrally disposed within a trilobal sheath152.

FIG. 11 shows a core 151 which is foamed or cellular, reference number55 designating one of the many closed cell dispersed therein. FIG. 10illustrates another embodiment of a sheath-core filament of thisinvention where the sheath 156 surrounds or provides a matrix for aplurality of spaced-apart parallel cores 157 of the higher-meltingfilament component (a). In FIG. 12, two, spaced-apart, parallel cores161, 162 of dissimilar plastic components (a) are disposed within thesheath 163. FIG. 13 shows a filament having central core 164 and sheath165 with generally rectangular or elliptical cross-sections.

FIGS. 15, 16, and 17 illustrate various embodiments of side-by-sidemulticomponent filaments of this invention. In FIG. 15, layers 66 of thehigher melting plastic component (a) and layers 67 of the lower meltingplastic component (b) are alternately disposed in the filament. FIG. 16illustrates a side-by-side bicomponent filament composed of the highermelting component 70 and lower melting component 71. In FIG. 17, thebicomponent filament is generally rectangular in cross section andcomposed of a stripe or ribbon 68 of the higher melting plasticcomponent (a) and a contiguous strip 69 of the lower melting plasticcomponent (b).

FIG. 18 illustrates a bundle or aggregation 73 of bicomponentsheath-core filaments 74 (such as those shown in FIG. 7). FIG. 19 showshow the corresponding bundle of FIG. 18 looks upon melt-bonding, namely,bundle 73' which is made up of sheath-core filaments 74' in the bondedform, there being fillets 76 of the lower-melting sheath componentformed at the points of contact. Similarly, FIG. 20 shows the exteriorof the unbonded contiguous filaments 74 and FIG. 21 shows the exteriorof the corresponding bonded filaments 74' with the fillets 76 formed atthe points of contact thereof.

FIG. 22 illustrates a mat 77 of this invention that can be cut from thefinished webbing 43 of FIG. 1B.

FIG. 23 illustrates how the mat of FIG. 22 can be bonded on its lowersurface to a backing 78 to form a backed or supported mat 79. Thebacking 78 can be a thermoplastic material which can be pre-embossed onits lower surface with a pattern, such as that shown, for example, toimpart slip resistance to the mat 79.

FIG. 24 illustrates how the mat of FIG. 22 can be embossed on onesurface to form an embossed mat 81 having raised portions 82 andrecessed or depressed portions or channels 83, the dimensions of whichraised and recessed portions can vary.

FIG. 25 illustrates the toughness of the multicomponent filaments ofthis invention and the durable melt-bond obtained when an aggregation ofthe filaments are melt-bonded. In FIG. 25, a representative portion ofsuch an aggregation of filaments are shown after they were melt-bondedand subjected to a pulling stress. Upon exerting such stress, some ofthe melt-bonds remained intact, as depicted by intact melt bond 120between intersecting filaments 121 and 122, while other melt bondsbroke, as depicted by the remnant 123 of a broken melt-bond, and some ofthe filaments broke, one of which, depicted as 124, attenuated before itbroke.

FIG. 26 illustrates two of the multicomponent filaments 131, 132 of thisinvention which can be covered or coated with abrasive mineralparticulate or grains 133 bonded to the thermoplastic component (b)defining the surface of the filaments. An aggregation or web of suchabrasive-coated filaments can be used as an abrasive pad or tool.

Thermoplastics (including blends of two or more thermoplastics) whichcan be used to prepare the multicomponent filaments of this inventionare melt-extrudable, normally solid, synthetic organic polymers. Theparticular application of multicomponent filaments of this invention maydictate which melt-extrudable thermoplastics are selected therefor,based on their melting points. In addition to melting point as aselection guide, the desired toughness of a particular filament, andapplication thereof may also serve as a selection guide. Preferably thethermoplastic precursors can be melt-extruded into filaments that, whencooled and solidified, are tough in their undrawn state and do notembrittle upon subsequent thermal steps, such as melt-bonding,embossing, and backing. The level or degree of adhesion between the twocomponents of the multicomponent filament at their interface(interfacial adhesion) is important to consider when selecting the typeof polymer(s) for the sheath or core. While good interfacial adhesion isnot necessary to achieve a tough, macrodenier, multicomponent filament,such adhesion may be desirable for abrasion resistance and toughness.

We have found that not all thermoplastics will be useful in making thetough multicomponent filaments of this invention. Specifically, commonthermoplastics used to make drawn, bicomponent, textile fibers may notproduce tough, macrodenier, multicomponent filaments in their undrawnstate. For example, some polyethylene terephthalates and somepolypropylenes, said to be useful in making drawn bicomponent binderfibers, have been found by us to produce undrawn, macrodenier,bicomponent fibers which are brittle and weak, thereby exhibiting poorflexibility and toughness.

Thermoplastics which can be used to prepare the multicomponentmacrofilaments of this invention are preferably melt-extrudable above38° C. and generally are filament-forming. The thermoplastics useful forcomponent (b) must melt at a temperature lower than the melting point ofcomponent (a) (e.g. at least 15° C. lower). Furthermore, thethermoplastics for both components (a) and (b) are preferably thosewhich have a tensile strength of 3.4 MPa or greater and elongation tobreak of 100% or greater, as measured by ASTM D882-90. Each of suchthermoplastics is tough, preferably having a work of rupture, as definedby Morton and Hearle in Physical Properties of Textile Fibers, 1962, of1.9×10⁷ J/m³ or greater, as measured from the area under thestress-strain curve generated according to ASTM D882-90 for bothcomponents (a) and (b). Additionally, both components preferably haveflex-fatigue resistance, or folding endurance, greater than 200 cyclesto break, as measured according to ASTM D2176-63T, before and after heataging or any melt-bonding step. The flex-fatigue resistance can beperformed on a 15 mm×140 mm strip of film of the thermoplastic, asoutlined in Instruction Booklet No. 64-10, Tinius Olsen Testing MachineCo., Easton Road, Willow Grove, Pa. As mentioned earlier, the filamentsof this invention are durably melt-bondable. A simple test of themelt-bondability of the filaments, herein referred to as FilamentNetwork Melt-Bond Strength Test, has been devised to measure suchmelt-bondability and is described below.

The Filament Network Melt-Bond Strength Test Employs afilament-supporting jig in the form of a 3 inch×4 inch×3/8 in (7.7cm×10.2 cm×1 cm) rectangular block of aluminum, having a centralrectangular opening extending from one face to the other and measuring11/4 inch×21/4 inch (3.2 cm×5.7 cm). Eight straight grooves of equallength are cut in the top face of the block and extending from thecentral opening to the edges of the block to support a network to beformed by two sets of intersecting identical specimens or segments of afilament whose melt-bonded strength is to be measured and compared withthat of the filament itself. One set of the grooves consists of a pairof parallel, longitudinally-cut grooves, 1/2 inch (1.2 cm) apart anddeep enough to accommodate the width or diameter of the filamentspecimen placed therein and extending across the block from one edgethereof to the opening and in alignment with a second pair of linegrooves extending from the opening to the opposing edge of the block.The other set of the grooves consist of two similar pairs of grooves,3/4 inch (1.5 cm) apart, extending transversely across the block fromone edge to the opposing edge. The specimens of the filament to bemelt-bonded are cut long enough to be laid into and extend beyond thegrooves and each is pulled taut to remove slack (and without drawing) toform a network or grid (in the form of a "tic-tac-toe" figure) andmaintained in that position with pieces of pressure-sensitive adhesivetape, e.g., masking tape, 1 inch (2.54 cm) wide. The filament-jigassembly is placed in a circulating-air oven and heated sufficiently tocause melt-bonds to form, one bond at each of the four points ofintersection (over the central opening) of the specimens of filaments.The assembly is removed from the oven and allowed to stand at roomtemperature to cool and solidify the melt-bonds. The masking tape isthen removed and the strength of the melt-bonds in the bonded filamentnetwork is then determined by using a Chatillon force gauge, type 719,and a stiff, round rod, such as a 1/4 inch (0.5 cm) diameter pencil orwood dowel. The hook of the gauge is placed so as to grasp a firstspecimen at its center between the two melt bonds that bond it to twoother specimens and permit the gauge to be pulled longitudinally by handaway from the network. The rod is placed vertically within the rectangleformed in the network and held against a second specimen opposite thefirst specimen and centrally between the two melt bonds that bond thesecond specimen to said two other specimens. With the gauge hook and rodso-positioned, the gage is pulled until a melt bond or a networkfilament breaks, and the gauge reading is noted at the time of suchbreak. This test is repeated 1-5 times with other specimens of the samefilament and the gauge readings at break are recorded together with thenature of the breaks (i.e., melt-bond break or filament break). Theaverage force is calculated. A durably melt-bonded filament has, asmentioned, a melt-bond whose breaking force exceeds 1.4 MPa, based onthe cross-section area of the filament before breaking stress isapplied.

Preferred properties of thermoplastic polymers useful as components oftough, undrawn, macrodenier, multicomponent filaments of this invention,e.g., sheath-core bicomponent filaments, are set forth in Table 1,together with test methods for determining such properties.

                  TABLE I                                                         ______________________________________                                        Material Property Component (a)                                                                             Component (b)                                   ______________________________________                                        Melting Point, °C.                                                                       at least 15° C.                                                                    >38° C.                                    (ASTM D2117) greater than                                                      melting point of                                                              Component (b)                                                                Tensile Strength, MPa  ≧3.4 ≧3.4                                (ASTM D882-90)                                                                Elongation, % ≧100 ≧100                                         (ASTM D882-90)                                                                Work of Rupture, J/m.sup.3 ≧1.9 × 10.sup.7 ≧1.9                                       × 10.sup.7                                  (Morton and Hearle, loc. cit.)                                                Flex Fatigue Resistance, Cycles to >200 >200                                  Break (ASTM D2176-63T, modified                                               to flex under 2.46 MPa constant                                               stress)                                                                     ______________________________________                                    

Melting temperature or point (the temperature that a material turns froma solid to a liquid), tensile strength at break, and elongation at breakfor the thermoplastics to be used in making the multicomponent filamentsof this invention may be found in published information on thethermoplastics, such as vendor literature, polymer handbooks, ormaterial databases. The tensile strength, elongation, toughness (work ofrupture), and the flex-fatigue resistance of such thermoplastic can bedetermined on pressed, molded, or extruded film or sheet that has notbeen drawn and which has been heat aged at the desired melt-bondingtemperature and time to be used in melt-bonding the filaments.

Examples of thermoplastic polymers which can be used to form components(a) and (b) of the macrofilainents of this invention include polymersselected from the following classes, which preferably meet the criteriaset forth in Table 1: polyolefins, such as polyethylenes,polypropylenes, polybutylenes, blends of two or more of suchpolyolefins, and copolymers of ethylene and/or propylene with oneanother and/or with small amounts of copolymerizable, higher, alphaolefins, such as pentene, methylpentene, hexene, or octene; halogenatedpolyolefins, such as chlorinated polyethylene, poly(vinylidenefluoride), poly(vinylidene chloride), and plasticized poly(vinylchloride); copolyester-ether elastomers of cyclohexane dimethanol,tetramethylene glycol, and terephthalic acid; copolyester elastomerssuch as block copolymers of polybutylene terephthalate and long chainpolyester glycols; polyethers, such as polyphenyleneoxide; polyamides,such as poly(hexamethylene adipamide), e.g., nylon 6 and nylon 6,6;nylon elastomers; such as nylon 11, nylon 12, nylon 6,10 and polyetherblock polyamides; polyurethanes; copolymers of ethylene, or ethylene andpropylene, with (meth)acrylic acid or with esters of lower alkanols andethylenically-unsaturated carboxylic acids, such as copolymers ofethylene with (meth)acrylic acid, vinyl acetate, methyl acrylate, orethyl acrylate; ionomers, such as ethylene-methacrylic acid copolymerstabilized with zinc, lithium, or sodium counterions; acrylonitrilepolymers, such as acrylonitrile-butadiene-styrene copolymers; acryliccopolymers; chemically-modified polyolefins, such as maleic anhydride-or acrylic acid-grafted homo- or co-polymers of olefins and blends oftwo or more of such polymers, such as blends of polyethylene andpoly(methyl acrylate), blends of ethylene-vinyl acetate copolymer andethylene-methyl acrylate; and blends of polyethylene and/orpolypropylene with poly(vinyl acetate). The foregoing polymers arenormally solid, generally high molecular weight, and melt-extrudablesuch that they can be heated to form molten viscous liquids which can bepumped as streams to the extrusion die assembly and readily extrudedtherefrom under pressure as the multicomponent filaments of thisinvention. The same thermoplastic substance can serve as component (b),e.g., a sheath, in one embodiment of the filaments and as component (a),e.g., a core, in another embodiment of the filaments.

Examples of some commercially-available polymers useful in the practiceof this invention are those sold as Elvax™ ethylene-vinyl acetatecopolymers, such as Elvax™ 40W, 4320, 250, and 350 products; EMAC™ethylene-methyl acrylate copolymer, such as EMAC™ DS-1274, DS-1176,DS-1278-70, SP 2220 and SP2260 products; Vista Flex™ thermoplasticelastomer, such as Vista Flex™ 641 and 671; Primacor™ ethylene-acrylicacid copolymers, such as Primacor™ 3330, 3440, 3460, and 5980 products;Fusabond™ maleic anhydride-g-polyolefin, such as Fusabond™ MB-110D andMZ-203D products; Himont™ ethylene-propylene copolymer, such as Himont™KS-057, KS-075, and KS-051P products; FINA™ polypropylene, such as FINA™3860X product; Escorene™ polypropylene such as Escorene™ 3445;Vestoplast™ 750 ethylene-propylene-butene copolymer; Surlyn™ ionomer,such as Surlyn™ 9970 and 1702 products; Ultramid™ polyamide, such asUltramid™ B3 nylon 6 and Ultramid™ A3 nylon 6,6 products; Zytel™polyamide, such as Zytel™ FE3677 nylon 6,6 product; Rilsan™ polyamideelastomer, such as BMNO P40, BESNO P40 and BESNO P20 nylon 11 products;Pebax™ polyether block polyamide elastomer, such as Pebax™ 2533, 3533,4033, 5562 and 7033 products; Hytrel™ polyester elastomer, such asHytrel™ 3078, 4056 and 5526 products. The above-described ELVAX, EMAC,Primacor, Rilsan, Pebax, Hytrel and Surlyn products may be used, aloneor as blends, as component (b); and the above described Vistaflex,Fusabond, Himont, Escorene, Fina, Ultramid and Zytel products can beused alone or as blends of two or more to form component (a). Exemplarycombinations of these polymers are set forth in Table 2.

                  TABLE 2                                                         ______________________________________                                        Combination                                                                            Component (b)   Component (a)                                        ______________________________________                                        I        75 wt % ELVAX 350                                                                             Ultramid B3                                             25 wt % EMAC SP 2220                                                         II 75 wt % ELVAX 350 Himont KS-075                                             25 wt % EMAC SP 2220                                                         III 75 wt % ELVAX 350 40 wt % Vestoplast 750                                   25 wt % EMAC SP 2220 60 wt % Escorene 3445                                   IV BMNO P40 Zytel FE 3677                                                     V Hytrel 5526 Zytel FE 3677                                                   VI Pebax 3533 Ultramid A3K                                                  ______________________________________                                    

Blends of two or more polymers to form component (a) or (b) of thefilaments of this invention may be used to allow the custom modificationof material properties such that the components meet the performancetargets required for a particular application.

Some blends (two of which are believed to be novel) of thermoplasticpolymers useful in this invention have been found to possess synergisticflex-fatigue resistance. Such blends have one or more property valueslisted in Table 1 which are surprisingly superior over thosecorresponding property values of the individual thermoplastic polymersthat are in the blends. The blends can be prepared by simple mixing ofthe thermoplastic polymers in the appropriate ratios. One such blend isa blend of 85 to 15 wt % poly(ethylene-vinyl acetate), such as Elvax™copolymer, with 15 to 85 wt % poly(ethylene-acrylic acid), such asPRIMACOR™ polymer, which blend is useful to form a sheath of asheath-core bicomponent fiber of this invention. Such blend exhibitsbetter flex-fatigue resistance than either poly(ethylene vinyl acetate)or poly(ethylene-acrylic acid) per se. Subsequent heat-aging, however,will degrade these flex-fatigue properties, but the heat-aged blendstill meets the property values of Table 1. The poly(ethylene-vinylacetate) component of the blend generally will have a weight averagemolecular weight, M_(w), of 50,000 to 220,000 and will have 5 to 45 mol% of its interpolymerized units derived from the vinyl acetate comonomerand the balance of units from ethylene. The poly(ethylene-acrylic acid)component of the blend generally will have a M_(w) of 50,000 to 400,000and have 1 to 10 mol % of its interpolymerized units derived fromacrylic acid and the balance from ethylene.

Another such novel blend is a blend of 20 to 70 wt %poly(ethylene-propylene-butene) terpolymer having M_(w) of 40,000 to150,000 and derived from equally large amounts of butene and propyleneand a small amount of ethylene), such as Vestoplast™ 750 polymer, with80 to 30 wt % isotactic polypropylene, such blend having highly superiorflex fatigue properties as compared to Vestoplast 750 or isotacticpolypropylene components per se. Surprisingly, heat aging was found toimprove the blend's flex-fatigue resistance. Such blends are useful informing the core of sheath-core filament of this invention.

Another blend that which can be used in making the multicomponentfilaments is a blend that contains from 15 to 85 wt %poly(ethylene-vinyl acetate) and 85 to 15 wt % poly(ethylene-methylacrylate), such as EMAC™ polymer. The poly(ethylene-vinyl acetate)component of this blend can have a molecular weight and composition likethat described above. The poly(methyl acrylate) component can have aM_(w) of 50,000 to 200,000 and 4 to 40 mol % of its interpolymerizedunits derived from the methyl acrylate comonomer. The blend has superiorflex fatigue resistance as compared to poly(ethylene-vinyl acetate)component per se or poly(ethylene-methyl acrylate) component per se.Subsequent heat-aging of the blend further increased flex fatigueresistance above that of the blend prior to heat aging. Such blend isalso useful in forming the core of sheath-core filament of thisinvention.

The above-described synergistic blends also have utility in the form offilm, tapes, or tubing, which involve no heat-bonding, and the blendscan also be used as heat-bonding film.

The multicomponent filaments of this invention and/or articlesincorporating such filaments may be modified by a number ofpost-extrusion operations to further enhance utility. Some examples ofsuch operations are the following.

Hot Quench Bath Process (for Melt-bonding)

In the preparation of articles incorporating the macrodenier,multicomponent filaments of this invention, the temperature of thequench bath described above, e.g., in FIGS. 1A and 1B, may be anelevated temperature to permit durable melt-bonding of the filaments,thus eliminating the need for a thermal bonding step after the filamentsare withdrawn from the quench bath. Because of the multicomponent natureof the filaments of this invention, the quench medium in this operationcan be heated to a temperature above the melting point of component (b)but below that of component (a). If the web of such filaments ismaintained at this temperature, the tackiness or flowability of thestill hot component (b) of the filaments is retained, while the nowessentially-solidified component (a) provides dimensional stability tothe filaments, and, as a result, component (b) has time to melt-bond atthe initial tack-bonding sites and provide similar if not equal strengthto that achieved in a post-quench thermal bonding step that otherwisewould be necessary for durable melt bonding. In contrast, singlecomponent filaments cannot be heated to these elevated quenchtemperatures without seriously distorting or destroying theiras-quenched, tack-bonded filamentary structure obtained at lower quenchtemperatures. This operation, wherein the quench medium can both quenchand simultaneously permit melt-bonding, does away with the need foradditional bondings step(s). The bath medium for this operation can beselected to match the various filament components and their melttemperatures. The medium may be water or other heat-exchange fluids,such as inert silicone oil or inert fluorochemical fluids. The bath forthis operation may be heated by a variety of methods, e.g., electricalimmersion heaters, steam, or other liquid heat-exchange means. Forexample, steam heat may be used to heat a water quench bath to atemperature below the boiling point of water but to a temperature hotenough to melt thermoplastics like polyvinylacetate when used forcomponent (b) of the filaments, while nylon 6 may be used for component(a) which will be quenched at these temperatures. The time andtemperature that a web of such multicomponent filaments experiences inthe elevated-temperature bath will also affect interfilament bondstrength. In conveying the web through the elevated-temperature quenchmedium and any associated rolls and guiding devices, it may be desirableor necessary to support the web continuously through the medium. It mayalso be advantageous to add a further cooling station to satisfactorilycool the heated web prior to any additional conveying, handling, orprocessing.

Embossing Webs

Embossing the melt-bonded, open, nonwoven webs of the macrodenier,multicomponent filaments of this invention is another way of providing achange in either the surface appearance of a web article or in thefunctionality of the article. Embossing the web article can change thephysical appearance of the structure, e.g., by adding a recessed gridpattern or message (e.g., "THINK SAFETY") or a flattened edge to a mat.Additionally, articles comprising the filaments can be embossed bypassing such an article between patterned or embossing rolls while thearticle is still hot and soft from the melt-bonding step and before itis completely cooled. Such an embossed article is shown in FIG. 24. Thisembossing operation may be utilized to reinforce a web of themulticomponent filaments in both the machine direction and crossdirection. The multicomponent filament nature of the webs considerablyimproves the ease by which embossing for a nonwoven filamentary web maybe achieved. Embossing a pattern may comprise heating a multicomponentfilament web (without undue distortion or collapse of the web) and thenimparting the pattern from a suitably-shaped platen under pressure whichalso functions to cool the hot web. Alternatively, a heated platen canbe used to locally soften and compress a cool web without distorting theremaining uncompressed and unheated web. Desired patterns of either acontinuous or noncontinuous nature can be embossed readily without theneed for an additional and later reheating step and without undesiredcollapse of the web structure.

In one method of forming such a patterned web, the above-described HotQuench Bath Process can be utilized in conjunction with a pair ofpatterned or embossing rolls that are located after web formation so asto pattern the so-formed web while component (b) of the multicomponentfilaments thereof is still hot and tacky and while the web is stilleasily deformable but yet bonded. This method isolates the web-embossingstep from the web-formation step where any excessive surface or wavemotion of the bath, that could arise from complex patterns of a surfaceembossing roll interacting with the bath surface interface, wouldultimately cause the resulting web to be nonuniform. The embossing rollsmay be contained within the quench bath or may even be located outsideof the quench bath but impart their patterning while the web is stillhot and before it is cooled to ambient conditions. A patterned web mayalso be formed by embossing bonded web emerging from a hot air-bondingoven (in cases where hot bath-bonding may not be desirable) with anembossing roll, which typically will be chilled. Because of themulticomponent filament nature of the web, web temperatures higher thanthe collapse temperature of component (b) of the filaments can beachieved so that embossing with excellent flow characteristics can beaccomplished without undesired web collapse or distortion. This processpatterning would be much more difficult if not impossible withmonocomponent fibers that require bonding with an additional bondingagent(s) and web collapse would be a limiting factor.

Foaming Multicomponent Filaments

By dispersing a chemical blowing agent, such as azodicarabonamide,sodium bicarbonate, or any other suitable gas-generating orfoam-inducing agent, physical or chemical, to a composition used to forma component of the macrodenier, multicomponent filaments of thisinvention, a foamed or cellular structure can be imparted to some or allof the components of the filaments. Such foaming may be used to alterthe material properties (e.g., resiliency, specific gravity, adsorptioncharacteristics, antislip properties, etc.) of the articles made fromthe foamed or cellular multicomponent filaments. Such foaming may tendto swell the thickness of the individual filaments as well as theoverall thickness of webs formed from these filaments. A surprising andunexpected result of macrodenier, multicomponent filaments of thisinvention with foamed cores is the superior tensile strength of websformed from such foamed filaments as compared to web made with unfoamedmulticomponent filaments.

Laminating

The macrodenier, multicomponent filaments or webs of this invention maybe laminated to one or more preformed elements or backing, such asthermoplastic films or sheets. These elements can be solid or porous (inthe case of a foamed film). The backing may act as an impervious barrierto either particulates or fluids as in the case of backed floor mats ofopen, non-woven webs of the multicomponent filaments, or the backing mayact as a reinforcing agent imparting dimensional stability to such mats.The melt-bondable nature of the multicomponent filaments of thisinvention is particularly useful in achieving their excellentself-bonding to such backings without the need for additional bondingagents. The bonding and laminating temperatures can be sufficient tocause the filaments to become hot and tacky to allow fusion between thebacking and filaments while component (a) thereof is above themelt-bonding temperature. Although not restricted to like materials,better bonding can be achieved between similar materials, that is, whenthe laminating backing is of the same thermoplastic composition ascomponent (b) of the multicomponent filament of this invention.Additionally, the backing may be embossed, prior to lamination, with asecondary pattern, for example, raised pegs or projections, to impart atexture or frictional aspect to the backing or the backing may beembossed as a result of a pattern transferred from a supporting carrierweb, for example, a metal grid or mesh, that carries the backing and webthrough a melt-bonding oven to produce a backed web as describedhereinabove and shown in FIG. 23.

The backing may also be thermoformed prior to lamination. The laminationmay be carried out by a variety of methods, such as illustrated in FIG.1C.

In another lamination process, such as shown in FIG. 1D, a coolpreformed backing may be used instead of the cast backing illustrated inFIG. 1C, and sufficient tack-bonding can be developed between the coolbacking and the web to allow the laminate to be conveyed to the bondingoven where durable melt-bonding can be achieved. Alternatively, the HotQuench Bath Process described above can be used to durably melt-bondmulticomponent filaments of the laminate.

In another lamination process, a preformed thermoplastic backing may bepositioned below the web just prior to the melt-bonding oven, wherebythe weight of the web in contact with the backing is sufficient toobtain the durable melt-bond of the web-backing laminate. Theselaminations can be considered to be ambient lamination without anyundesired or added pressures, but these laminations can also be formedusing compressive forces to deform hot webs so as to form additionalembossing (described hereinbefore) in combination with laminatingprocess.

Abrasive Articles

Abrasive articles can be made using the macrodenier, multicomponentfilaments of this invention or webs thereof These articles can be usedfor abrasive cutting or shaping, polishing, or cleaning of metals, wood,plastics, and the like. Additionally, coating abrasive particulate orgrains on the multicomponent filament surfaces can provide antislip orfriction. Current methods of creating an abrasive article as taught inU.S. Pat. No. 4,227,350, for example, typically rely on first coating asuitable substrate with a durable binder resin and, while it is stilltacky, then coating thereon abrasive particles or other materials, andfinally curing the abrasive or antislip composite structure to achievedurability, toughness, and functionality. Such a process typicallyrequires high performance resin systems that contain solvents and otherhazardous chemicals that necessitate additional careful monitoring toensure adequate cure with minimization of residual ingredients as wellas sophisticated pollution control schemes to control harmful solventemissions. The tough, multicomponent filaments of this invention allowsimplification to the overall abrasive- or particle-holding bindersystems by elimination of solvent-coating techniques, the ability to use100% solids systems instead, and elimination even of the need foradditional bonding agent in the cases where a prebond resin system mustbe used prior to any abrasive binder resin system. The multicomponentfilaments of this invention can simultaneously provide bonding and "makecoat" capability. Materials suitable for the abrasive particulatecomponent can be granules of regular or nonregular shape, of virtuallyany size, and selected from a broad variety of classes of natural orsynthetic, abrasive, mineral particulate, such as silicon carbide,aluminum oxide, cubic boron nitride, ceramic beads or grains such asCubitron™ abrasive materials, and plastic abrasive grains, as well asagglomerates of one or more of these materials. The ultimate use of theabrasive article will determine what materials are suitable forcomponent (b) of the multicomponent filament of such article.

Different methods of applying or coating the abrasive particulate on orto the filaments or webs of this invention can be used. Because of themulticomponent nature of the filaments of this invention, the highermelting point component (a) thereof allows structural integrity of thefilaments while allowing component (b) to retain its hot, tacky naturewhen the filaments are heated in a melt-bonding oven. By sprinkling,dropping, blowing or otherwise coating the abrasive particulates ontothe hot, tacky surface of the filaments, the particulates will adhere tosuch surface. Depending on the heat capacity, crystallinity, and meltingpoint of component (b), adhesion of room temperature or cool abrasiveparticulates can occur. Enhanced adhesion can occur when abrasivemineral particulate is preheated prior to dropping onto the hotcomponent (b) surface such that localized cooling is minimized. Adhesionto higher melting point thermoplastics is especially enhanced bypreheating the abrasive mineral. In addition, surface treatments of theabrasive particulates may also enhance adhesion, for example, by asilane surface treatment. Another method of coating filaments or webs ofthis invention is passage of either the filaments or previouslyprebonded webs thereof into a fluidized bed of heated abrasive mineralparticulate. This process has the particular advantage of moreforcefully pushing the hot abrasive mineral into heated component (b).After cooling, the abrasive particulates are adhered onto and intocomponent (b). A further size coat of suitable resin, such as apolyurethane or resole phenolic resin, may be used to further lock theabrasive particulate to the surface of the multicomponent filament orwebs thereof.

Filamentary Structures

The multicomponent nature of the filaments of this invention may also beadvantageously used to enhance bonding when articles or webs in the formof filamentary structures, for example, as generally taught by U.S. Pat.Nos. 4,631,215 (Welygan et al.), 4,634,485, and 4,384,022 (Fowler) arefabricated from both straight and undulating or spiral filaments.Bonding occurs when the undulating or spiraling, hot, extruded,multicomponent filaments contact adjacent straight filaments and thenare quenched in a cooling bath to retain the shape of the so-formedfilamentary structure. The multicomponent nature of the filamentsprovides an unexpected advantage by allowing component (a) thereof toprovide a structural role in supporting the shape of the web of suchfilaments in either a post-formation melt-bonding step or by utilizingthe above-described Hot Quench Bath Process without the need for anyadditional process steps. In this fashion a tough, durable web offilamentary structure of multicomponent filaments can be prepared.

Fire Retardancy

As mentioned hereinbefore, fire retardant additives may be incorporatedor dispersed in the filaments of this invention. Examples of suchadditives are ammonium polyphosphate, ethylenediamine phosphates,alumina trihydrate, gypsum, red phosphorus, halogenated substances,sodium bicarbonate, and magnesium hydroxide. Such additives can beblended with the particulate thermoplastic precursor of components (a)and/or (b) of the filaments of this invention or can be added to themelts thereof in the melt extruders used to prepare them. Preferablysuch additives, where used to impart fire retardancy to filaments ofthis invention, are incorporated only in a component (a) which does nothave an external surface that defines the material-air boundary of thefilaments such as the core of bicomponent sheath-core filaments. Byso-incorporating the fire retardant additive in the core of thefilament, the melt-bonding capability of the sheath, component (b), andthus the durability of the resulting melt-bonded structure, remainuncompromised, even if a high amount of the fire retardant additive isused. The particular fire retardant additive used for this purpose andthe amount thereof to be incorporated will depend upon the particularfilament to be made fire retardant, the particular thermoplasticsthereof, and the application to be made of the filament. Generally, theamount of fire retardant additive, such as magnesium hydroxide, will be10 to 40 wt % or more, based on the total weight of the fire retardantadditive and filament or, functionally stated, an amount sufficient torender the filament fire retardant as determined by ASTM D-2859-76.

EXAMPLES

The following examples are meant to be illustrative of this inventionand objects and advantages thereof, and should not be construed aslimiting the scope of this invention. The measurement values given inthese examples are generally average values except where otherwisenoted.

Example 1

Extrusion, quenching, and web collection equipment like that of FIG. 1Bwas used to make open, non-woven web of concentric sheath-corebicomponent filaments like those whose cross-section is shown in FIG. 7.In this example, an amount of 98 parts of Ultramid B3 nylon-6 pellets(previously dried under a nitrogen blanket at 100° C.) were blended with2 parts nylon pigment pellet concentrate (supplied by Reed SpectrumCo.). The blend was extruded as a stream of viscous core melt through a38 mm single-screw extruder having a 36/1 L/D ratio (length/diameter)and neck tube into a coextrusion die assembly of the castellation type,like that illustrated in FIGS. 2A, 2B, at a temperature of 280-290° C.and at a rate of 20.3 kg/hr to form the core of sheath-core bicomponentfilaments of this invention. Specifications of the extrusion dieassembly are given in Table 3.

                  TABLE 3                                                         ______________________________________                                        Number of rows of die orifices                                                                      5                                                         Orifice row spacing 4.064 mm                                                  Orifice spacing 6.350 mm                                                      Orifice diameter 0.572 mm                                                     Orifice L/D 4/1                                                               Number of orifices 75                                                         Castellation diameter 2.997 mm                                                Castellation width 0.737 mm                                                   Castellation gap 0.254 mm                                                     Vertical channel diameter 1.524 mm                                          ______________________________________                                    

Elvax 350 ethylene-vinyl acetate copolymer and EMAC SP2220ethylene-methyl acrylate copolymer were blended together at a weightratio of 3/1, respectively. The resulting blend was extruded,simultaneously with the extrusion of the above-described polymer coremelt, as a stream of viscous, sheath melt through a 30 mm single-screwextruder having a 30/1 L/D ratio into the same coextrusion extruder dieassembly as described above, at a temperature of 230-240° C. and at arate of 30.7 kg/hr to form the sheath of the bicomponent filaments.

The resulting bundle of hot, tacky, macrodenier, sheath-core bicomponentfilaments continuously extruded from the extrusion die assembly wasallowed to fall freely in quiescent ambient air for a distance of about300 mm before coiling and advancing as a web in a water quench bath(about 25 to 32° C.) containing 0.03 wt % dioctyl-sodium sulfosuccinatesurfactant, where the filaments cooled and solidified with theinterengaged filaments tack- or spot-bonded together in an open web. Thefalling filaments made glancing contact on a quench roll partiallyimmersed in the quench bath and thereby differentially quenched in thequench bath, as described in said U.S. Pat. No. 4,351,683. The filamentswere advanced through the bath at a take-away speed of 2.1 meters perminute, producing open nonwoven web having a densified layer portionfrom contact with the quench roll and an opposing nondensified layerportion adjacent the noncontacting side of the bundle. The finaldiameter of the quenched bicomponent filaments ranged from 0.712 to0.737 mm with a 60/40 sheath to core ratio by volume. The web offilaments had a weight of 1.8 kg/m². The web was removed from the bathand air-dried. Filaments were removed from the tack-bonded web and themelt-bondability thereof was determined according to the FilamentNetwork Melt-Bond Strength Test; filament breakage occurred at 8.9 N or22.4 MPa. The filaments in the dried web were made to durably melt-bondat their points of contact by heating the web in a circulating-air ovenat 150 to 160° C. for 3 minutes. The melt-bonded web was removed fromthe oven and allowed to cool to ambient conditions. The resulting open,nonwoven web comprising undrawn, durably melt-bonded, continuous,intermeshed, macrodenier, multicomponent filaments, with a sheath-corevolume ratio of 60/40, was 15.3 mm thick and generally resembled the webillustrated in FIG. 22.

Example 2

Using the process described in Example 1 to make concentric sheath-core,macrodenier bicomponent filaments and web thereof, Escorene 3445polypropylene pellets and Vestoplast 750 terpolymeric olefin pelletswere blended together at a weight ratio of 1/1 with 12 wt % magnesiumhydroxide flame retardant concentrate (LR 84827, supplied by AmpacetCo.) and 2 wt % olefin pigment concentrate (supplied by Reed SpectrumCo.). The blend was extruded at 230 to 240° C. and at a rate of 27.5kg/hr to form the core of sheath-core bicomponent filaments of thisinvention. Elvax 350 ethylene-vinyl acetate copolymer and EMAC SP2220ethylene-methyl acrylate copolymer were blended together at a weightratio of 3/1, respectively. The blend was simultaneously extruded at 230to 240° C. and at a rate of 27.5 kg/hr to form the sheath of thesheath-core bicomponent filaments of this invention. The final diameterof the quenched macrodenier filaments was 0.712 to 0.737 mm and filamentbreakage occurred at 5.8N or 14.6 MPa.

Using thermal-bonding conditions of Example 1, the resulting open,nonwoven, melt-bonded web comprising undrawn, durable, continuous,intermeshed, macrodenier sheath-core filaments with a sheath to coreratio of 50/50, had a web weight of 2.0 kg/m², was 15.6 mm thick andgenerally resembled the web illustrated in FIG. 22.

A sample of the web was found to be fire retardant when subjected to theflame retardancy test of ASTM D-2859-76, which corresponds to theFlammability Test of the U.S. Dept. of Commerce, DOC FF 1-70.

Example 3

Using the process described in Example 1 to make concentric sheath-core,macrodenier, bicomponent filaments and web thereof, Himont KS-075ethylene-propylene graft copolymer pellets were blended with 12 wt %magnesium hydroxide flame retardant concentrate (LR 84827 from AmpacetCo.) and 2 wt % olefin pigment concentrate (from Reed Spectrum Co.). Theresulting blend was extruded at a rate of 27.5 kg/hr to form the core ofthe sheath-core bicomponent filaments of this invention. Elvax 350ethylene-vinyl acetate copolymer and EMAC SP2220 ethylene-methylacrylate copolymer were blended together at a weight ratio of 3/1,respectively. The resulting blend was simultaneously extruded at atemperature of 230 to 240° C. and at a rate of 27.5 kg/hr to form thesheath of the sheath-core bicomponent filaments of this invention. Thefinal diameter of the quenched bicomponent filaments was 0.737 to 0.787mm.

Using thermal bonding conditions of Example 1, the resulting open,durably melt-bonded web, comprising undrawn, continuous, intermeshed,macrodenier filaments with a sheath-to-core weight ratio of 50/50, had aweb weight of 2.4 kg/m², was 16.3 mm thick, and generally resembled theweb illustrated in FIG. 22.

Example 4

Using the process described in Example 1 to make concentric sheath-core,macrodenier, bicomponent filaments and web thereof, and sheath and corematerials as described in Example 3, a continuous web was made offilaments having diameters of 0.737-0.787 mm (after a free fall of 310mm) and that were advanced in the quench bath at a take away speed of2.0 m/min. The water bath temperature was raised to 80° C., at whichpoint melt-bonding of the filaments at their points of contact occurredover the initial spot- or tack-bonding of the web formed at the lowerbath temperature. The web was withdrawn from the bath, cooled andair-dried. The resulting open, permanently melt-bonded web comprisingundrawn, durable, continuous, intermeshed, macrodenier, sheath-corefilaments with a sheath-core volume ratio of 50/50, had a web weight of2.1 kg/m², was about 15 mm thick and generally resembled the webillustrated in FIG. 22. Surprisingly no further heat treatment of theweb was needed to produce a durably melt-bonded web equivalent to theweb subject to the oven bonding process, as shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                       Web Tensile Strength, N/cm                                     Condition        Cross Tensile                                                                            Length Tensile                                    ______________________________________                                        Water Temp. = 34° C.                                                                    18.3       4.6                                                 (no oven bonding)                                                             Water Temp. = 80° C. 90.4 70.7                                         Water Temp. = 34° C. 67.1 44.1                                         (oven bonded 3 min at 150° C.)                                       ______________________________________                                    

In another run, using the process described in Example 1 to makeconcentric sheath-core, macrodenier, bicomponent filaments and webthereof, Zytel FE3677 nylon 6,6 pellets (previously dried under anitrogen blanket at 100° C.) were extruded at 280 to 290° C. and at arate of 19.3 kg/hr to form the core of the sheath-core bicomponentfilaments of this invention. Rilsan BMNO P40 nylon 11 pellets wereextruded at a temperature of 230 to 240° C. and at a rate of 23.7 kg/hrto form the sheath of the sheath-core bicomponent filaments of thisinvention. Continuous webs having filament diameters of 0.406 to 0.440mm after free falling 310 mm and a web weight of 0.98 kg/m² were made.After water quenching and air drying, this spot- or tack-bonded web wasconveyed into another quench bath containing a high temperature siliconefluid (Product #17,563-B of the Aldrich Chem. Co., CAS No. 63148-58-3)heated to 180° C. The web was held for 2 min in the bath to causedurable melt-bonding of the filaments to take place.

Example 5

Webs made as described in Examples 1, 2, and 3 were heated in acirculating-air oven at 160° C. for 3 min, removed from the circulatingair oven, and, while still hot, the web was laid on a cool, flatsurface, and was embossed on its top surface with a checkboard patternusing an embossing plate having a raised pattern that allowedcompression or embossing of selected areas of the hot web while havingsufficient clearance so as not to distort or compress the remainingareas of the web. The embossing plate was applied to the top surface ofthe web with a force of about 1 kg/cm². The duration of embossing was 30seconds. Upon air-cooling of the hot web, the resulting embossed patternwas permanent and consisted of undeformed web of durably melt-bondedfilaments and having squares about 2 by 4 cm separated by compressed orembossed channels having a width of 1 cm. The embossed webs areillustrated in FIG. 24.

Example 6

Web made in an 80° C. temperature quench bath as described in Example 4was passed between the nip of a rotating embossing roll (replacing roll44a of FIG. 1B) at 2 m/min and a smooth backup roll (designated 44b ofFIG. 1B). The web still being hot was thereby embossed on its top with acheckboard pattern as in Example 5.

Example 7

An open, durably melt-bonded web comprising undrawn, durable,continuous, intermeshed, macrodenier filaments with a sheath-core ratioof 50/50, having a web weight of 2.1 kg/m², and thickness of 16.3 mm,made as described in Example 3, was placed on a silicone rubber-coveredbuffer cloth. The layered combination was put onto the platen surface ofa 6 KW Thermatron™ radio frequency (RF) press. A 9.5 mm thick magnesiumetched-plate having a design comprised of the raised lettering "3M,"about 6.1 mm high and having a surface area of about 32 cm, was placedon the top surface of the web-cloth combination. The press was closedand pressure applied with an air piston having a diameter of 15.24 cmand pressurized at 0.66 MPa. The RF heating cycle of the press was 10sec. at 30% power with a cooling cycle (under pressure) of 7 sec. Thepress was opened and the resulting web had the recessed lettering "3M"clearly embossed on the top surface of the web without any unduedistortion of the portion web surrounding the lettering.

Example 8

Using the process described in Example 1 to make concentric sheath-core,macrodenier bicomponent filaments and web thereof, Ultramid B3 nylon 6pellets (previously dried under a nitrogen blanket at 100° C.) wereextruded at 280-290° C. and at a rate of 3.4 kg/hr to form the core ofthe sheath-core bicomponent macrodenier filaments of this invention.Elvax 350 ethylene-vinyl acetate copolymer and EMAC SP2220ethylene-methyl acrylate copolymer were blended together at a weightratio of 3/1, respectively; the blend was simultaneously extruded at 230to 240° C. and at a rate of 15.9 kg/hr to form the sheath of thesheath-core bicomponent filaments of this invention. Continuous webshaving filament diameters of 0.712 to 0.747 mm after free-falling 300 mmand a web weight of about 0.75 kg/m² were made of the sheath-corefilaments. Instead of forming a single core within the sheath, adifferent distribution plate (item 18 of FIG. 2B) was used having threeorifices (each 3.81 mm in diameter) arranged in a triangular patternwith the orifices at the apices of an equilateral triangle but yetlocated within the flow boundary of the vertical channel (item 27 ofFIG. 2B). The centerline of each orifice was 4.572 mm from thecenterline of the vertical channel. The core melt was directed to saidorifices to allow three core components to be formed within the sheathcomponent of each macrodenier filament. The cross-section of such afiber is illustrated in FIG. 10.

Example 9

A batch of Himont KS-075 ethylene-propylene graft copolymer pellets wereextruded through a 38 mm extruder having a 36/1 L/D ratio and a necktube into a coextrusion die assembly having slot-shaped, major and minorextrusion die orifices capable of forming a filamentary structureconsisting of bicomponent sheath-core filaments, rectangular in crosssection. The structure was otherwise in the form of a central regularlyundulated filament extruded via the major slots and surrounded andbonded to a plurality of straight, parallel, spaced, filaments, extrudedvia the minor slots and forming a cage for the undulated filament, asdescribed in U.S. Pat. No. 4,631,215 and shown in FIG. 7 thereof, whichdescription is incorporated herein by reference. The extrusion wascarried out at a temperature of 230-240° C. and at a rate of 18.2 kg/hr.Specifications of the extrusion die assembly similar to that used inExample 1 are given in Table 5.

                  TABLE 5                                                         ______________________________________                                        Major slot width      2.591   mm                                                Major slot height 7.874 mm                                                    Minor slot width 1.803 mm                                                     Minor slot height 8.636 mm                                                    Slot spacing 7.163 mm                                                         Number of major slots 6                                                       Number of minor slots 7                                                       Castellation width 0.61 mm                                                  ______________________________________                                    

Elvax 350 ethylene-vinyl acetate copolymer and EMAC SP2220ethylene-methyl acrylate copolymer were blended together at a weightratio of 3/1, respectively. The blend was extruded at 230 to 240° C. andat a rate of 32.6 kg/hr to form the sheath of the sheath-corebicomponent filaments of this invention. The as-extruded filamentarystructure consisting of melt-extruded, bicomponent, undulated andstraight filaments from the extruder die assembly was allowed to fallfreely therefrom for a distance of 108 mm before entering into the waterquench bath where they were quenched as described in U.S. Pat. No.4,631,215. The finished web weighed about 3.8 kg/m².

Example 10

Multilayer side-by-side filaments having a cross-section like thatillustrated in FIG. 15, were prepared by melt-extruding two differentthermoplastics, designated "A" and "B" for clarity in description, infive alternating layers, that is, ABABA, using extrusion, quenching, andweb collection equipment like that illustrated in FIG. 1A. To form the"A" layers, Surlyn 1702 ionomer resin was extruded through a 38 mmsingle-screw extruder having a 36/1 L/D ratio and neck tube into the dieassembly at a temperature of 285-290° C. and a rate of 9.1 kg/hr. Toform the "B" layers, Elvax 250 ethylene-vinyl acetate copolymer wasextruded through a 30 mm single-screw extruder having a 30/1 L/D ratiointo the coextrusion die assembly at a temperature of 205-275° C. and ata rate of 7.7 kg/hr. Details of the coextrusion die assembly to formthese multilayer filaments are given in Table 6.

                  TABLE 6                                                         ______________________________________                                        Number of rows of die orifices                                                                       4                                                        Orifice row spacing 5.715 mm                                                  Orifice spacing 3.175 mm                                                      Orifice diameter 0.889 mm                                                     Orifice L/D 5                                                                 Number of orifices 120                                                        Vertical channel diameter 1.080 mm                                            Vertical flow passageway width 0.381 mm                                       Vertical flow passageway spacing 6.350 mm                                     Orifice cavity entrance width 1.080 mm                                        Orifice cavity entrance length 4.445 mm                                     ______________________________________                                    

Continuous webs comprised of these quenched five-layer filaments werethus made having filament diameters of 0.432 to 0.508 mm after freefalling 300 mm and a web weight of 1.27 kg/m². The filaments weredifferentially quenched in the bath, which contained 0.03 wt % dioctylsodium sulfosuccinate surfactant, at a take-away speed of 2.1 meters perminute. The resulting open, nonwoven web of coiled five-layeredmacrodenier filaments had a densified surface from contact with thequench roll and an opposing undensified surface on the noncontactingside of the filament bundle.

Example 11

The process described in Example 1 was used to make four open, non-wovenwebs of concentric sheath-core, macrodenier bicomponent filaments withthe same sheaths but with the cores being different for each web. Forthese webs, Escorene 3445 polypropylene pellets and Vestoplast 750terpolymeric olefin pellets were first blended together at a weightratio of 1/1 with 12 wt % magnesium hydroxide flame retardantconcentrate (LR 84827 supplied by Ampacet Co.). Four separate coreprecursor batches using this preblend were then prepared by adding tothree of the batches a chemical blowing agent, Kempore™ 125 (anazodicarbonamide supplied by Uniroyal Chemical Co.), the quantity of thechemical blowing agent used in each batch being different. The blendswere extruded in separate batches at 230 to 240° C. and at a rate of27.5 kg/hr to form the core of sheath-core bicomponent filaments of thisinvention. For the sheath, Elvax 350 ethylene-vinyl acetate copolymerand EMAC SP2220 ethylene-methyl acrylate copolymer were blended togetherat a weight ratio of 3/1, respectively. The resulting blend wassimultaneously extruded with each of the separate core precursor batchesdescribed above at a temperature of 230 to 240° C. and at a rate of 28.4kg/hr to form the sheath of the sheath-core bicomponent filaments ofthis invention. The hot, tacky, melt-extruded, sheath-core filamentswere allowed to fall freely in quiescent air for a distance of about 290mm before coiling and advancing in the water quench bath as a web. Thefilaments were differentially quenched in the bath (which contained 0.03wt % dioctyl sodium sulfosuccinate surfactant) at a take-away speed of2.4 meters per min. The resulting open, nonwoven web of coiled,continuous filaments had a densified surface from contact with thequench roll and an opposed non-densified surface from the noncontactingside of the bundle of filaments. A cross section of the sheath-corefilaments under a microscope revealed a cellular structure as depictedin FIG. 11 with the cellular content varying with the amount of chemicalblowing agent. The tensile strength of the quenched web containingchemical blowing agent was unexpectedly stronger than that of the webwhich contained no chemical blowing agent even though the thickness andweight of the webs remained relatively constant. The final diameter ofthe quenched bicomponent filaments, web thickness, and tensile data withthe amount of chemical blowing agent present are detailed in Table 7.

The tensile strength of the various webs were measured using an Instrontensiometer with a crosshead speed of 50.8 cm/min. Sample size was 5 cmacross by 18 cm. Tensiometer jaw spacing was 5 cm. The webs were notheat bonded. The results of such measurements, set forth in Table 7,surprisingly show that the use of a blowing agent significantlyincreased the strength of the tack-bonded web as compared to web madefrom bicomponent filaments that did not contain blowing agent.

                  TABLE 7                                                         ______________________________________                                              Amount of                                                                  foaming Web Web Filament Cross Length                                        Web agent Weight Thickness Diameter Tensile, Tensile,                         No. (wt %) (kg/m.sup.2) (mm) (mm) (N/cm) (N/cm)                             ______________________________________                                        1     0        2.51    21.3   .711   30.1  10.5                                 2 0.1 2.43 19.2 .787 52.9 20.5                                                3 0.2 2.56 22.0 .787 60.2 27.8                                                4 0.4 2.57 22.6 1.041 74.1 42.9                                             ______________________________________                                    

Example 12

Web made as described in Example 2 but not heat bonded was separatedinto helical strands, chopped using a guillotine cutter into 25-38 mmstaple, sheath-core filaments, and the staple was air-dropped onto atray of Teflon™ plastic to produce a random three-dimensional array ofthe staple filaments. The array of staple filaments was heated in acirculating-air oven at 150° C. for 3 min. to durably melt-bond thestaple at points of contact and produce a tough, open, nonwoven web ofthe bonded staple filaments.

Example 13

Web made as described in Example 1 and as illustrated in FIG. 22 wasplaced onto a tray of Teflon™ polymer and heated in a circulating-airoven at 150° C. for 3 min. Immediately after removal from the oven, 80grit particulate aluminum oxide mineral was dropped onto the hot, tacky,top surface of the web until it was essentially covered. The coated webwas cooled to produce a bonded abrasive web of the sheath-corefilaments. Similarly, Polyhard Type III plastic (30-40 mesh) abrasiveblasting media was applied to the surface of the above web ofbicomponent sheath-core filaments.

Using the process described in Example 1 to make concentric sheath-corebicomponent filaments and web thereof, Zytel FE3677 nylon 6,6 pellets(previously dried under a nitrogen blanket at 100° C.) were extruded at304-310° C. and at a rate of 11.4 kg/hr to form the core of thesheath-core bicomponent filaments of this invention. Rilsan BMNO™ P40nylon 11 pellets were extruded at a temperature of 218 to 240° C. and ata rate of 20.7 kg/hr to form the sheath of the sheath-core bicomponentfilaments of this invention. The filament bundle was allowed to fallfreely for a distance of 250 mm before coiling and advancing into thewater quench bath. The filaments were quenched in a water quench bath ata take-away speed of approximately 5.3 meters per minute producing anon-woven web having a slightly densified surfaces from contact with thequench rolls and a resulting web weight of 0.98 kg/m² and web thicknessof 22-24 mm. The final diameters of the quenched filaments were0.48-0.51 mm. The web was heated in a circulating-air oven for 3 min. at215° C. Silicon carbide abrasive mineral (80 grit) was also heated in analuminum pan at 215° C. in the same oven for 3 minutes and sprinkledonto the still hot web. The mineral-coated web was allowed to cool uponremoval from the oven. The mineral was sufficiently adhered to the webto allow moderate handling without dislodging the mineral. Apolyurethane size-coat comprising Adiprene™ BL-35 (67.69 wt %polyurethane prepolymer, mixed with a 35% solution of methylene-diaminein 2-ethoxyethanol acetate) was prepared for subsequent overcoating ofthe mineral-coated webs. The size-coat mixture was heated slightly toassist in mixing and reduce viscosity. The previously preparedmineral-coated webs were die-cut into 10 cm diameter disks. Two of thesedisks (having 80-grit mineral) were coated with size and then spun toremove excess coating. The disks were then cured at 150° C. for 20minutes. The finished disks were attached to a heavy-duty, rotary, airtool, capable of approximately 18,000 rpm, with a self-tighteningmandrel. A small amount of topical lubricant was applied to minimizesmearing. The disks were tested by abrading a stainless steel strip.Wheel integrity was very good without web breakup or dislodging of themineral. Abrasion of the stainless steep strip was observed as would beexpected of an aggressive abrasive wheel.

Using the same coating procedures as described above, 180 grit siliconcarbide abrasive was also applied to the surface of the web ofbicomponent sheath-core filaments comprised of Rilsan BMNO™ P40 nylon 11sheath and Zytel™ FE3677 nylon 6,6 core and tested in the same fashion.Table 8 summarizes the composition of these composite abrasive articles.

                  TABLE 8                                                         ______________________________________                                                         Wt., g/154 cm.sup.2                                            Web                                                                                          80 Grit S/C                                                                           180 Grit S/C                                         ______________________________________                                        Web only           10.47     10.47                                              Web and mineral coat 41.22 19.65                                              Web and mineral and size coat 50.14 23.61                                   ______________________________________                                    

Example 14

A variety of web or mat composites, Lots D to I, similar to thatillustrated in FIG. 23 (but without the embossed pattern on thebacking), were prepared from different combinations of webs comprised ofmacrodenier, sheath-core bicomponent filaments of this invention andcertain sheet backings. The sheet backings consisted of either blends ofElvax 350 and EMAC SP2220 or blends of Elvax 260 and Primacor 3460, asdetailed in Table 10. In addition, the sheet backing of Lot I was foamedusing a chemical blowing agent.

Each of the unfoamed sheet backings was about 0.762 mm in thickness andwas prepared by extruding, at a temperature of about 183° C., a mixtureof components, as described in Table 10, from a 63.5 mm single-screwextruder, having an L/D ratio of 30/1, through a 508 mm film die into afilm falling 75 mm before being contacted by a set of polished, chilled,steel nip rolls. The rolls were chilled to 15° C. and the sheetcollected at a line speed of 1.3 meters/min.

The foamed film backing was about 0.5 mm in thickness and was preparedby extruding at a temperature of about 190° C. a mixture of components,as described in Table 10, from a 89 mm single-screw extruder, having anL/D ratio of 36/1 containing a single-flighted, two-stage screw havingtwo dispersive mixing sections, through a static Kenics™ mixer which was28.5 mm in diameter and 279 mm in length and consisted of nine staticelements, and finally through a 1290 mm film die into a film fallingabout 4mm before contacting a polished, chilled, steel roll. The 610 mmdiameter roll was chilled to 12° C. and the film collected at a linespeed of 7.6 meters/min.

In making each of the web or mat composites D, E, F, H, I, the firstprepared webs were placed on the top surface of the prepared films, thecombinations as described in Table 10, to form a two-layer combination.This combination was then passed through a two-zone, circulating-airoven (7.6 m long) having first zone at a temperature of 155° C. and asecond zone at a temperature of 130° C. Each composite was moved throughthe oven on a carrier belt (a mesh with 6 mm square openings) at a linespeed of 3 m/min. The composites were then removed from thecirculating-air oven and cooled to ambient conditions. The resultingcomposites were durably melt-bonded at the web-backing interface and atthe contiguous or crossover points of contact of the individual webfilaments.

A second sample of composite F was similarly treated but at 165° C. forabout 3.5 min. The resulting composite had a pronounced mesh patternembossed on the lower surface of the backing, providing slip resistanceto the composite.

Lamination of the backing sheet to the web of Lot G was alsoaccomplished by feeding the previously formed backing sheet onto thequench roll and, while melt-extruding the bicomponent filaments by theprocess described in Example 3, allowing the hot and tacky bicomponentmacrodenier filaments to differentially quench against the sheet.Surprisingly the resulting web was durably melt-bonded to the backing,resulting in a tough, durable backed mat.

                  TABLE 10                                                        ______________________________________                                                  Amounts of Ingredients, wt %                                          Lot                                                                         Ingredients D      E       F    G     H    I                                  ______________________________________                                        Sheath                                                                          Elvax 350     73.5   73.5  73.5 73.5  73.5 73.5                               EMAC SP 2220 24.5 24.5 24.5 24.5 24.5 24.5                                    Pigment conc. 2.0 2.0 2.0 2.0 2.0 2.0                                       Core                                                                            Escorene 3445 43                           43                                 Vestoplast 750 43     43                                                      Himont KS-075  77.5  77.5                                                     Fusabond 110D  8.5  8.5                                                       Ultramid B3   100  100                                                        Mg(OH).sub.2.sup.(a) 12.0 12.0  12.0  12.0                                    Pigment conc. 2.0 2.0  2.0  2.0                                             Backing Sheet                                                                   Elvax 350     75.0   75.0  75.0                                               EMAC SP 2220 25.0 25.0 25.0                                                   Elvax 260    80.0 80.0 19.8                                                   Primacor 3460    20.0 20.0 79.2                                               Foaming agent.sup.(b)      1.0                                              ______________________________________                                         .sup.(a) The Mg(OH).sub.2 was a mixture of equal parts of Mg(OH).sub.2 an     Elvax 350.                                                                    .sup.(b) The foaming agent was Safoam ™ RIC50.                        

Example 15

To demonstrate that the processes of this invention do not impartsignificant orientation to the filaments produced thereby (i.e., theyare essentially undrawn) or articles made therefrom, the unoriented,macrodenier sheath-core filaments of Lots J, K, and L were prepared andanalyzed for degree of orientation. The filaments were prepared usingthe process described in Example 1 except for the differences notedhereafter. Web of the filaments of Lot J was prepared in the samefashion as Example 3 except that the sheath contained 2 parts of pigmentconcentrate per 100 parts of sheath precursor and the core was preparedfrom a blend of 77.5 wt % Himont KS-075 ethylene-propylene graftcopolymer; 8.5 wt % Fusabond MB-110D linear, low density, maleicanhydride-graft-polyethylene; 12 wt % magnesium hydroxide concentrate(equal amounts of magnesium hydroxide and Elvax 260 ethylene-vinylacetate copolymer), and 2 wt % color pigment concentrate. Web offilaments of Lot K was prepared in the same fashion as Example 2 exceptthat the sheath contained 2 parts of pigment concentrate per 100 partsof sheath precursor and the magnesium hydroxide fire retardant of thecore component was dispersed in Elvax 260 instead of polypropylene. Thetow of filaments of Lot L was prepared in the same fashion as Example 1except that the sheath contained 2 parts of pigment concentrate per 100parts of sheath precursor. Instead of allowing the filaments tooscillate or coil and form a web as in the webs of filaments of Lots Jand K, the take away speed used to make filaments of Lot L was increasedto equal the extrusion speed such that straight filaments resulted. Thefinal diameter of the quenched, sheath-core filaments was 0.712-0.737mm.

The filaments were pulled by hand (without attenuation) from tack-bondedwebs of filaments of Lots J and K and from the tow of filaments of LotL. The pulled filaments were examined by flat plate x-ray diffractionanalysis for molecular orientation using a transmission pinhole camera(a Statton camera as described Experiments in Polymer Science, Edward A.Collins, Jan Bares and Fred W. Billmeyer, p. 194, John Wiley and SonsInc., 1973) with nickel-filtered Cu Kα radiation. The individualfilaments were aligned vertically and parallel with respect to thephotographic film. The so-analyzed undrawn filaments were then pulledunder ambient conditions to the natural draw ratio, that is, elongated(stretched) to the point where further elongation would result inbreakage of the filament. The so-drawn filaments were then re-examinedby the x-ray diffraction analysis described above.

Examination of the resultant photographic images provided informationregarding crystallinity and orientation of the filaments. Crystallinitywas evidenced by the presence of rings or arcs. Orientation wasevidenced by the presence of arcs, the smaller the arc length, thegreater the orientation. Totally unoriented material display concentricrings, called Debye rings (cf. Fred W. Billmeyer Jr., Textbook ofPolymer Science, 2nd Ed., p. 114, John Wiley and Sons, Inc., 1971). Theresults of such analysis is set forth in Table 11 and demonstrate thatthe undrawn macrodenier multifilaments of this invention are unoriented.

                  TABLE 11                                                        ______________________________________                                        Filaments       X-ray pattern analysis                                        LOT   Geometry  Undrawn filament                                                                            Drawn filament                                  ______________________________________                                        J     coiled    uniform Debye rings                                                                         arcs (well oriented)                                (unoriented)                                                                K coiled uniform Debye rings arcs (well oriented)                               (unoriented)                                                                L straight uniform Debye rings arcs (highly oriented)                           unoriented                                                                ______________________________________                                    

Example 16

Durable, individual, unoriented, multicomponent, macrofilaments wereprepared using the process generally outlined in Example 1 except thatthe speed of the take-away rolls (FIG. 1B) was adjusted to allow eachfilament to coil slightly without intermingling or contacting adjacentfilaments and forming a web as they were quenched and withdrawn from thequench bath. The resulting individual filaments resembled thoseillustrated in FIG. 4 and show a helical twist to the filament.

In another run using the process generally outlined in Example 1 and thematerials of Example 13, straight, individual, undrawn macrofilamentswere prepared. The speed of the take-away roll (FIG. 1B) was increasedto equal the extrusion speed to allow the filaments to be withdrawnstraight but yet undrawn and filly quenched from the quench bath.

Example 17

Four different films, ranging in thickness from 0.3 to 0.38 mm, wereprepared by blending 80 to 20 wt % Elvax 260 ethylene vinyl-acetatecopolymer with 20 to 80 wt % Primacor 3460 ethylene-acrylic acidcopolymer, extruding the blend at 220° C. from a 32 mm single-stageextruder having an L/D of 30/1, through a film die having a 0.5 mmorifice into a film falling 3 mm before being contacted by a set ofpolished, chilled, nip rolls. The rolls were chilled to 22° C. and thefilms were collected at a line speed of 1.9 meters/minute. Film sampleswere allowed to equilibrate at ambient conditions for 168 hours, afterwhich films were evaluated for flex-fatigue resistance according to ASTMD2176-63T, modified to provide a constant 1.14 MPa load. Table 12illustrates the synergistic improvement of the films made from theblends in flex-fatigue resistance over the films made from the unblendedpolymers. For comparison, a film of Elvax 260 copolymer and a film ofPrimacor 3460 copolymer were similarly prepared and evaluated.

                  TABLE 12                                                        ______________________________________                                        Film Composition,                                                               Amt. of polymer, wt % Flex Fatigue Resistance,                                   Elvax 260   Primacor 3460                                                                            Cycles to Break,                                    Film copolymer copolymer Before Heat Aging                                  ______________________________________                                        A    0           100        68,000                                              B 20 80 250,000*                                                              C 40 60 250,000*                                                              D 60 80 250,000*                                                              E 80 20 250,000*                                                              F 100 0 150,000                                                             ______________________________________                                         *Test stopped at 250,000 cycles. No failure was noted.                   

Similarly, blends of 50 to 80 wt % Elvax 350 ethylene vinyl-acetatecopolymer and 50 to 20 wt % Primacor 3460 ethylene-acrylic acidcopolymer were extruded into films according to the process describedabove and evaluated according to ASTM D2176-63T, modified to provide aconstant 1.14 MPa load. Table 13 illustrates the effect of heat aging atabout 149° C. for 3 minutes.

                  TABLE 13                                                        ______________________________________                                        Film Composition,       Flex Fatigue Resistance,                                Amt. of polymer, wt %  Cycles to Break                                            Elvax 350                                                                              Primacor 3460                                                                              Before  After Heat                                  Film copolymer copolymer Heat Aging Aging                                   ______________________________________                                          H 80 20 200,000  18,400                                                       I 50 50 307,600 155,800                                                     ______________________________________                                    

The data of Tables 12 and 13 show that the blends of Films B, C, D, E,H, and I would be particularly useful as components (a) or (b) in thefabrication of multicomponent filaments of this invention because oftheir desirable flex-fatigue resistance.

Example 18

Four different films, ranging in thickness from 0.2 to 0.66 mm, wereprepared by melt blending 50 g batches of blends of Elvax 350ethylene-vinyl acetate copolymer and 80 to 20 wt % EMAC SP2220ethylene-methylacrylate copolymer, using a Brabender mixer fitted with asigma blade, at 130° C. and 40 RPM for 5 minutes. Each molten polymerblend was removed from the Brabender and pressed between metal platescoated with Teflon™ plastic to form film, using a hydraulic press at130° C. and 6.89 MPa pressure. The plate-film assemblies were removedfrom the press and quenched in 16° C. water, the film was removed andallowed to stand in ambient air for about 1 week. The films wereevaluated for flex-fatigue resistance according to ASTM D2176-63T,modified to provide a constant stress of 2.46 MPa. For comparison, filmsof the unblended polymer components were similarly prepared andevaluated. Table 14 sets forth actual flex-fatigue resistancemeasurements and illustrates the synergistic improvement in flex fatigueresistance of the films of the blends over polymer components per seboth before and after heat aging at about 149° C. for 3 minutes. Heataging of compositions K, M, and N increased flex life.

                  TABLE 14                                                        ______________________________________                                        Film Composition,       Flex Fatigue Resistance,                                Amt. of polymer, wt %  Cycles to Break                                            Elvax 350                                                                              EMAC SP2220  Before  After Heat                                  Film copolymer copolymer Heat Aging Aging                                   ______________________________________                                        J     0        100          24,000  13,000                                      K 20 80 31,000 97,000                                                         L 40 60 106,000 70,000                                                        M 60 40 46,000 86,000                                                         N 80 20 7,000 69,000                                                          O 100 0 18,000 8,000                                                        ______________________________________                                    

Example 19

Five different films ranging in thickness from 0.25 to 74 mm, wereprepared by melt-blending 30 to 90 wt % Escorene 3445 isotacticpolypropylene with 10 to 70 wt % Vestoplast 750ethylene-propylene-butene copolymer, according to the process of Example18, except the blends were mixed at 210° C. in the Brabender mixer. Thefilms were evaluated for flex-fatigue resistance according to ASTMD2176-63T, modified to provide a constant stress of 2.46 MPa. Table 15sets forth actual flex-fatigue measurements and illustrates theoutstanding synergistic improvement in flex-fatigue resistance of thefilms (after heat aging at about 149° C. for 3 min.) of the blends overthe films of the unblended polymer components per se.

                  TABLE 5                                                         ______________________________________                                        Film Composition, Amt. of                                                       polymer, wt % Flex-Fatigue Resistance,                                           Escorene 3445                                                                             Vestoplast 750                                                                           Cycles to Break,                                    Film polymer polymer After Heat Aging                                       ______________________________________                                        P    0           100        **                                                  Q 30 70  16,000                                                               R 40 60 1,000,000*                                                            S 60 40 1,000,000*                                                            T*** 70 30 1,000,000*                                                         U 90 10 158,000                                                               V 100 0 196,000                                                             ______________________________________                                         *Tests stopped at 1,000,000 cycles. No failure was noted.                     **Broke immediately,                                                          ***The flexfatigue resistance cycles to break before heat aging of the        film of Lot T was 660,000.                                               

Various alterations and modifications of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention.

What is claimed is:
 1. Matting of the type used as floor coverings ordoor mats for building entrances comprising an open, nonwoven web of aplurality of filaments, the filaments each comprising:(a) first plasticcomprising synthetic plastic polymer; and (b) second plastic comprisinglower melting, synthetic thermoplastic polymer;the components (a) and(b) being, along the length of the filament, elongated, contiguous, andcoextensive in length, the component (b) defining all or at least partof the material-air boundary of said filament, the filaments in thematting having a linear density greater than 200 denier per filament andbeing durably melt-bonded at their points of intersection and contact.2. Matting according to claim 1 wherein said filaments are sheath-corefilaments, the core being said component (a) and the sheath being saidcomponent (b).
 3. Matting according to claim 2, wherein the component(a) is in the form of a plurality of cores of the same composition ordifferent compositions.
 4. Matting according to claim 2, wherein thecore and the sheath are concentric.
 5. Matting according to claim 2,wherein the core is cellular.
 6. Matting according to claim 1 wherein asurface of the matting has a slip resistant pattern.
 7. Mattingaccording to claim 1 further comprising a laminated backing.
 8. Mattingaccording to claim 1 wherein the filaments are sheath-core bicomponentfilaments having a linear density of 500 to 20,000 denier per filament,and each filament comprising the following components:(a) a central corecomprising as the first plastic nylon; and (b) a sheath comprising asthe second plastic a blend of ethylene-vinyl acetate copolymer andethylene-methyl acrylate copolymer.
 9. Matting according to claim 1wherein the filaments are sheath-core bicomponent filaments having alinear density of 500 to 20,000 denier per filament, and each filamentcomprising the following components:(a) a central core comprising as thefirst plastic a blend of polypropylene and ethylene-propylene-butenecopolymer; and (b) a sheath comprising as the second plasticethylene-vinyl acetate copolymer blended with ethylene-methyl acrylatecopolymer.
 10. Matting according to claim 1 wherein the filaments aresheath-core bicomponent filaments having a linear density of 500 to20,000 denier per filament, and each filament comprising the followingcomponents:(a) a core comprising as the first plastic nylon 6; and (b) asheath comprising as the second plastic polyester elastomer, polyetherblock polyamide elastomer, or nylon
 11. 11. Matting according to claim 1the filaments are in the form of side-by-side filaments.
 12. Mattingaccording to claim 11, wherein the components (a) and (b) areside-by-side alternate layers.
 13. Matting according to claim 1, whereinthe component (b) has a melting point of at least 15° C. below that ofcomponent (a).
 14. Matting according to claim 1 wherein the filamentshave a linear density of 500 to 20,000 denier per filament.
 15. Mattingaccording to claim 1 wherein the filaments are continuous.
 16. Mattingaccording to claim 1 wherein the filaments have a helical shape. 17.Matting according to claim 1 further comprising fire retardant dispersedin components (a) and/or (b).
 18. Matting according to claim 1, whereinthe components (a) and (b) have tensile strengths greater than or equalto 3.4 MPa, elongation greater than or equal to 100%, work of rupturegreater than or equal to 1.9×10⁷ J/m³ and a flex fatigue resistancegreater than 200 cycles to break; and wherein the component (b) has amelting point greater than 38° C.
 19. Matting according to claim 1wherein the component (a) comprises nylon 6 and said component (b)comprises ethylene-vinyl acetate copolymer.
 20. Matting according toclaim 1 wherein the component (a) comprises nylon 6 and said component(b) comprises ethylene-vinyl acetate copolymer blended withethylene-methyl acrylate copolymer.